Datagridview data error - Исправление ошибок и поиск оптимальных решений проблем

I am working on a Winforms app that displays a DataGridView, bound to some database table.

It allows inserting fresh entries in to it, and does some data validation.

When a required column is left blank, or one of the unique constraints is violated, the DataError event calls this function:

protected void _data_error(object sender, DataGridViewDataErrorEventArgs e)
{
    MessageBox.Show(this,e.Exception.Message,"Error");
    e.ThrowException = false;
    e.Cancel = false;
}

When the popup is closed, the new row that was being edited is removed.
When this is done to a row that has already been saved (an update operation) the row loses its changes and loses focus.
I assume this means I need to signal the application to keep the row editable, but I do not know how to do that.

Paradoxically, if I replace the event handler with a throw(e.Exception) the exception gets thrown to the wind and is picked up by the uncaught exception handler, but the new row is preserved after that window closes.

How can I preserve the new row on a DataError event?

Edit:

My next thought was to save the row and add it to the DataGridView’s data source after the MessageBox pops up.
That does not work because adding data to the data source add’s it as a committed row which throws an exception because of the invalid data vs keeping the data as an editable row so that validation doesn’t happen.

Источник

I’m trying to resolve an issue I’m experiencing with a DataGridView bound to a data object that includes a DataGridViewComboBoxColumn that is bound to a list on the data object to provide values for the drop down. The user should be able to add values to
the DataGridViewComboBoxColumn.

However, investigating in the debugger one finds the DataGridViewComboBoxCell’s Items list does not contain the item that was added to the data object (model) during edit of another cell, however, the cell’s DataSource List contains the correct values. In
addition, the DataGridViewComboBoxColumn’s Items collection contains the correct values. Why are the data-bound cell’s Items not being updated when the data object is updated?

I would appreciate any guidance on how to correctly perform this type of work.

The dataGridView1_CellValidating method has blocks of commented out code showing the various techniques I’ve tried while working to resolve this issue. The hack of setting the DataGridViewComboBoxCell’s DataSource to null and then back to the binding source
appeared to work, but upon further testing I discovered the issue still persists.

One can recreate the issue with the following steps:

Type «one» into the LeftElementName combobox of the first row
Click into the LeftElementName combobox of the second row
Click the dropdown button and select the value «one»
Click into the LeftElementName combobox of the third row
Click into the LeftElementName combobox of the second row
Type «two» into the LeftElementName combobox of the second row
Click into the LeftElementName combobox of the third row
1. The DataGridView fires a DataError event for the LeftElementName column of the second row — «DataGridViewComboBoxCell value is not valid».
Click the dropdown button and select the value «two»
Click into the RightElementName combobox of this row (the third row)
1. The DataGridView fires a total of 4 DataError events for the LeftElementName column of the third row — «DataGridViewComboBoxCell value is not valid».

MappingDialog.cs:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace ComboBoxBindingIssue
{
    public partial class MappingDialog : Form
    {
        private int _leftElementColIdx;
        private int _rightElementColIdx;
        private BindingSource _leftElementsBinding;
        private BindingSource _rightElementsBinding;

        #region Properties

        /// <summary>
        /// Gets or sets the model.
        /// </summary>
        public Mappings Model { get; set; }

        #endregion Properties

        /// <summary>
        /// Initializes a new instance of the MappingDialog class.
        /// </summary>
        public MappingDialog()
        {
            _leftElementColIdx = -1;
            _rightElementColIdx = -1;
            InitializeComponent();

            this.dataGridView1.CellValidating += new System.Windows.Forms.DataGridViewCellValidatingEventHandler(this.dataGridView1_CellValidating);
            this.dataGridView1.DataError += new System.Windows.Forms.DataGridViewDataErrorEventHandler(this.dataGridView1_DataError);
            this.dataGridView1.EditingControlShowing += new System.Windows.Forms.DataGridViewEditingControlShowingEventHandler(this.dataGridView1_EditingControlShowing);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            BindingSource binding1 = new BindingSource();
            binding1.DataSource = Model;
            binding1.DataMember = "Collection";

            // initialize the DataGridView
            this.dataGridView1.AutoGenerateColumns = false;
            this.dataGridView1.AutoSize = true;
            this.dataGridView1.DataSource = binding1;

            // initialize and add a column for the LeftElementName
            DataGridViewColumn leftElementCol;
            if (Model.LeftElements.Count > 0)
            {
                // initialize and add a combo box column for LeftElementName
                leftElementCol = new DataGridViewComboBoxColumn();
                ((DataGridViewComboBoxColumn)leftElementCol).DisplayStyle = DataGridViewComboBoxDisplayStyle.ComboBox;
                ((DataGridViewComboBoxColumn)leftElementCol).FlatStyle = FlatStyle.Flat;

                _leftElementsBinding = new BindingSource();
                _leftElementsBinding.DataSource = Model;
                _leftElementsBinding.DataMember = "LeftElements";
                ((DataGridViewComboBoxColumn)leftElementCol).DataSource = _leftElementsBinding;
            }
            else
            {
                // initialize and add a text box column for LeftElementName
                leftElementCol = new DataGridViewTextBoxColumn();
                leftElementCol.ReadOnly = true;
            }
            leftElementCol.DataPropertyName = "LeftElementName";
            leftElementCol.Name = "LeftElementName";
            _leftElementColIdx = this.dataGridView1.Columns.Add(leftElementCol);

            // initialize and add a column for the RightElementName
            DataGridViewColumn rightElementCol;
            if (Model.RightElements.Count > 0)
            {
                // initialize and add a combo box column for RightElementName
                rightElementCol = new DataGridViewComboBoxColumn();
                ((DataGridViewComboBoxColumn)rightElementCol).DisplayStyle = DataGridViewComboBoxDisplayStyle.ComboBox;
                ((DataGridViewComboBoxColumn)rightElementCol).FlatStyle = FlatStyle.Flat;

                _rightElementsBinding = new BindingSource();
                _rightElementsBinding.DataSource = Model;
                _rightElementsBinding.DataMember = "RightElements";
                ((DataGridViewComboBoxColumn)rightElementCol).DataSource = _rightElementsBinding;
            }
            else
            {
                // initialize and add a text box column for RightElementName
                rightElementCol = new DataGridViewTextBoxColumn();
                rightElementCol.ReadOnly = true;
            }
            rightElementCol.DataPropertyName = "RightElementName";
            rightElementCol.Name = "RightElementName";
            _rightElementColIdx = this.dataGridView1.Columns.Add(rightElementCol);

            // initialize and add a combo box column for Direction
            DataGridViewComboBoxColumn comboColumn = new DataGridViewComboBoxColumn();
            comboColumn.DataSource = Enum.GetValues(typeof(MappingDirection));
            comboColumn.DataPropertyName = "Direction";
            comboColumn.Name = "Direction";
            this.dataGridView1.Columns.Add(comboColumn);

            // resize the DataGridView columns to fit the newly loaded data
            this.dataGridView1.AutoResizeColumns();
        }

        private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            DataGridViewComboBoxEditingControl comboBox = e.Control as DataGridViewComboBoxEditingControl;
            if (comboBox != null
                && (comboBox.EditingControlDataGridView.CurrentCell.ColumnIndex == _leftElementColIdx
                || comboBox.EditingControlDataGridView.CurrentCell.ColumnIndex == _rightElementColIdx))
            {
                // remove an existing event-handler, if present, to avoid 
                // adding multiple handlers when the editing control is reused
                //comboBox.Validating -= new CancelEventHandler(comboBox_Validating);

                comboBox.DropDownStyle = ComboBoxStyle.DropDown;

                // add event-handler
                //comboBox.Validating += new CancelEventHandler(comboBox_Validating);
            }
        }

        private void comboBox_Validating(object sender, CancelEventArgs e)
        {
            // Attempt to get the values stored at a different point - didn't seem to resolve the issue
            DataGridViewComboBoxEditingControl comboBox = sender as DataGridViewComboBoxEditingControl;
            if (comboBox != null)
            {
                DataGridView dgv = comboBox.EditingControlDataGridView;
                // add value if it does not exist
                if (!String.IsNullOrWhiteSpace(comboBox.Text)
                    && !Model.LeftElements.Contains<String>(comboBox.Text))
                {
                    DataGridViewComboBoxColumn comboColumn = dgv.Columns[dgv.CurrentCell.ColumnIndex] as DataGridViewComboBoxColumn;

                    Model.LeftElements.Add(comboBox.Text);
                    comboColumn.DataSource = null;
                    comboColumn.DataSource = _leftElementsBinding;
                    dgv.CurrentCell.Value = comboBox.Text;
                    System.Diagnostics.Debug.WriteLine("t Added Value to LeftElements");
                }
            }
        }

        private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {
            System.Diagnostics.Debug.WriteLine(String.Format("dataGridView1_CellValidating: Row: {0}, Col: {1}, FormattedValue: {2}", e.RowIndex, e.ColumnIndex, e.FormattedValue));
            DataGridViewComboBoxCell dgvComboBoxCell = ((DataGridView)sender)[e.ColumnIndex, e.RowIndex] as DataGridViewComboBoxCell;
            if (e.ColumnIndex == _leftElementColIdx
                && dgvComboBoxCell != null
                && !String.IsNullOrWhiteSpace(e.FormattedValue.ToString())
                && !Model.LeftElements.Contains<String>(e.FormattedValue.ToString()))
            {
                // add new element item to model
                Model.LeftElements.Add(e.FormattedValue.ToString());

                // Attempt #1 - Following from advice in the DataBinding and DataGridView FAQs
                // reset the BindingSource data source in order to reset bindings
                // Note: the BindingSource provuides a level of indirection at both design-time and run-time
                // that alleviates the need for users to reset their bindings or merge data sets.
                //((DataGridViewComboBoxCell)((DataGridView)sender)[e.ColumnIndex, e.RowIndex]).DataSource = _leftElementsBinding;
                //((DataGridView)sender).CurrentCell.Value = e.FormattedValue;                    

                // Attempt #2 - Method descriptions seemed to describe exactly what I needed -
                // "Causes a control bound to the BindingSource to reread all the items in the list and refresh their displayed values."
                //_leftElementsBinding.ResetBindings(false);
                //_leftElementsBinding.ResetCurrentItem();
                //_leftElementsBinding.ResetItem(_mappings.LeftElements.Count - 1);

                // Attempt #3 - Thrashing around at this point – came across a forum post that mentioned this working for someone
                //((DataGridView)sender).CommitEdit(DataGridViewDataErrorContexts.Commit);

                // Attempt #4 - DataBinding FAQ states this is incorrect, however, it is the only thing I could find to get the DataGridViewComboBoxCell's
                // Items collection to match the correct list of values most of the time. The issue persists.
                // Note: resetting the binding in this manner does not seem correct, however, the cell's items collection is updated correctly when performed
                //((DataGridViewComboBoxCell)((DataGridView)sender)[e.ColumnIndex, e.RowIndex]).DataSource = null;
                //((DataGridViewComboBoxCell)((DataGridView)sender)[e.ColumnIndex, e.RowIndex]).DataSource = _leftElementsBinding;
                dgvComboBoxCell.DataSource = null;
                dgvComboBoxCell.DataSource = _leftElementsBinding;
                ((DataGridView)sender).CurrentCell.Value = e.FormattedValue;

                System.Diagnostics.Debug.WriteLine("t Added Value to LeftElements");
            }
            else if (e.ColumnIndex == _rightElementColIdx
                && dgvComboBoxCell != null
                && !String.IsNullOrWhiteSpace(e.FormattedValue.ToString())
                && !Model.RightElements.Contains<String>(e.FormattedValue.ToString()))
            {
                // add new element item to model
                Model.RightElements.Add(e.FormattedValue.ToString());
                // Note: resetting the binding in this manner does not seem correct, however, the cell's items collection is updated correctly when performed
                dgvComboBoxCell.DataSource = null;
                dgvComboBoxCell.DataSource = _rightElementsBinding;
                ((DataGridView)sender).CurrentCell.Value = e.FormattedValue;

                System.Diagnostics.Debug.WriteLine("t Added Value to RightElements");
            }
        }

        private void dataGridView1_DataError(object sender, DataGridViewDataErrorEventArgs e)
        {
            /*MessageBox.Show(String.Format("({0},{1}): {2}", e.RowIndex, e.ColumnIndex, e.Exception.Message),
                "Data Error",
                MessageBoxButtons.OK,
                MessageBoxIcon.Warning);*/

            // the DataGridViewComboBoxCell's Items list does not contain the item that was added to the model during edit of another cell, however,
            // this cell's DataSource List contains the correct values. Why isn't the cell's Items being updated?

            System.Diagnostics.Debug.WriteLine(String.Format("({0},{1}): {2}", e.RowIndex, e.ColumnIndex, e.Exception.Message));
        }
    }
}

MappingDialog.Designer.cs:

namespace ComboBoxBindingIssue
{
    partial class MappingDialog
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.dataGridView1 = new System.Windows.Forms.DataGridView();
            this.buttonPanel = new System.Windows.Forms.Panel();
            this.cancelButton = new System.Windows.Forms.Button();
            this.okButton = new System.Windows.Forms.Button();
            ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit();
            this.buttonPanel.SuspendLayout();
            this.SuspendLayout();
            // 
            // dataGridView1
            // 
            this.dataGridView1.AllowUserToAddRows = false;
            this.dataGridView1.AllowUserToDeleteRows = false;
            this.dataGridView1.AllowUserToResizeRows = false;
            this.dataGridView1.AutoSizeColumnsMode = System.Windows.Forms.DataGridViewAutoSizeColumnsMode.AllCells;
            this.dataGridView1.BorderStyle = System.Windows.Forms.BorderStyle.None;
            this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
            this.dataGridView1.Dock = System.Windows.Forms.DockStyle.Fill;
            this.dataGridView1.EditMode = System.Windows.Forms.DataGridViewEditMode.EditOnKeystroke;
            this.dataGridView1.Location = new System.Drawing.Point(0, 0);
            this.dataGridView1.Name = "dataGridView1";
            this.dataGridView1.RowHeadersVisible = false;
            this.dataGridView1.ShowCellErrors = false;
            this.dataGridView1.ShowEditingIcon = false;
            this.dataGridView1.ShowRowErrors = false;
            this.dataGridView1.Size = new System.Drawing.Size(283, 232);
            this.dataGridView1.TabIndex = 0;
            this.dataGridView1.CellValidating += new System.Windows.Forms.DataGridViewCellValidatingEventHandler(this.dataGridView1_CellValidating);
            this.dataGridView1.DataError += new System.Windows.Forms.DataGridViewDataErrorEventHandler(this.dataGridView1_DataError);
            this.dataGridView1.EditingControlShowing += new System.Windows.Forms.DataGridViewEditingControlShowingEventHandler(this.dataGridView1_EditingControlShowing);
            // 
            // buttonPanel
            // 
            this.buttonPanel.Controls.Add(this.cancelButton);
            this.buttonPanel.Controls.Add(this.okButton);
            this.buttonPanel.Dock = System.Windows.Forms.DockStyle.Bottom;
            this.buttonPanel.Location = new System.Drawing.Point(0, 203);
            this.buttonPanel.Name = "buttonPanel";
            this.buttonPanel.Size = new System.Drawing.Size(283, 29);
            this.buttonPanel.TabIndex = 1;
            // 
            // cancelButton
            // 
            this.cancelButton.Anchor = ((System.Windows.Forms.AnchorStyles)((System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Right)));
            this.cancelButton.DialogResult = System.Windows.Forms.DialogResult.Cancel;
            this.cancelButton.Location = new System.Drawing.Point(196, 3);
            this.cancelButton.Name = "cancelButton";
            this.cancelButton.Size = new System.Drawing.Size(75, 23);
            this.cancelButton.TabIndex = 1;
            this.cancelButton.Text = "Cancel";
            this.cancelButton.UseVisualStyleBackColor = true;
            // 
            // okButton
            // 
            this.okButton.Anchor = ((System.Windows.Forms.AnchorStyles)((System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Right)));
            this.okButton.DialogResult = System.Windows.Forms.DialogResult.OK;
            this.okButton.Location = new System.Drawing.Point(115, 3);
            this.okButton.Name = "okButton";
            this.okButton.Size = new System.Drawing.Size(75, 23);
            this.okButton.TabIndex = 0;
            this.okButton.Text = "OK";
            this.okButton.UseVisualStyleBackColor = true;
            // 
            // MappingDialog
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.AutoSize = true;
            this.AutoSizeMode = System.Windows.Forms.AutoSizeMode.GrowAndShrink;
            this.ClientSize = new System.Drawing.Size(283, 232);
            this.Controls.Add(this.buttonPanel);
            this.Controls.Add(this.dataGridView1);
            this.MinimizeBox = false;
            this.Name = "MappingDialog";
            this.ShowIcon = false;
            this.ShowInTaskbar = false;
            this.Text = "Mapping";
            this.Load += new System.EventHandler(this.Form1_Load);
            ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit();
            this.buttonPanel.ResumeLayout(false);
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.DataGridView dataGridView1;
        private System.Windows.Forms.Panel buttonPanel;
        private System.Windows.Forms.Button okButton;
        private System.Windows.Forms.Button cancelButton;
    }
}

IMapping.cs:

using System;
using System.ComponentModel;

namespace ComboBoxBindingIssue
{
    /// <summary>
    /// Interface for mapping classes.
    /// </summary>
    public interface IMapping : INotifyPropertyChanged
    {
        /// <summary>
        /// Gets or sets the name of the left element.
        /// </summary>
        string LeftElementName { get; set; }

        /// <summary>
        /// Gets or sets the name of the right element.
        /// </summary>
        string RightElementName { get; set; }

        /// <summary>
        /// Gets or sets the mapping direction.
        /// </summary>
        MappingDirection Direction { get; set; }
    }
}

Mapping.cs:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;

namespace ComboBoxBindingIssue
{
    /// <summary>
    /// Defines a mapping between a left element and right element.
    /// </summary>
    public class Mapping : IMapping
    {
        private string _leftElementName;
        private string _rightElementName;
        private MappingDirection _direction;

        #region Properties

        /// <summary>
        /// Gets or sets the name of the left element.
        /// </summary>
        public string LeftElementName
        {
            get
            {
                return _leftElementName;
            }
            set
            {
                if (_leftElementName != value)
                {
                    _leftElementName = value;
                    OnPropertyChanged("LeftElementName");
                }
            }
        }

        /// <summary>
        /// Gets or sets the name of the right element.
        /// </summary>
        public string RightElementName
        {
            get
            {
                return _rightElementName;
            }
            set
            {
                if (_rightElementName != value)
                {
                    _rightElementName = value;
                    OnPropertyChanged("RightElementName");
                }
            }
        }

        /// <summary>
        /// Gets or sets the mapping direction.
        /// </summary>
        public MappingDirection Direction
        {
            get
            {
                return _direction;
            }
            set
            {
                if (_direction != value)
                {
                    _direction = value;
                    OnPropertyChanged("Direction");
                }
            }
        }

        #endregion Properties

        /// <summary>
        /// Event raised when a property is changed on the component.
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        /// Initializes a new instance of a Mapping class.
        /// </summary>
        /// <remarks>
        /// The left and right elements are set to String.Empty and
        /// the mapping direction is set to MappingDirection.None.
        /// </remarks>
        public Mapping()
            : this(String.Empty, String.Empty, MappingDirection.None)
        {
        }

        /// <summary>
        /// Initializes a new instance of a Mapping class.
        /// </summary>
        /// <remarks>
        /// The mapping direction is set to MappingDirection.None.
        /// </remarks>
        /// <param name="leftElementName">The name of the left element.</param>
        /// <param name="rightElementName">The name of the right element.</param>
        public Mapping(string leftElementName, string rightElementName)
            : this(leftElementName, rightElementName, MappingDirection.None)
        {
        }

        /// <summary>
        ///Initializes a new instance of a Mapping class.
        /// </summary>
        /// <remarks>
        /// IsValidLeftElementName and IsValidRightElementName are set to true.
        /// </remarks>
        /// <param name="leftElementName">The name of the left element.</param>
        /// <param name="rightElementName">The name of the right element.</param>
        /// <param name="direction">The mapping direction.</param>
        public Mapping(string leftElementName, string rightElementName, MappingDirection direction)
        {
            _leftElementName = leftElementName;
            _rightElementName = rightElementName;
            _direction = direction;
        }

        /// <summary>
        /// Fires a PropertyChanged event to notify clients that all properties changed.
        /// </summary>
        public void NotifyAllPropertiesChanged()
        {
            OnPropertyChanged(String.Empty);
        }

        /// <summary>
        /// Fires a PropertyChanged event to notify clients that a property value has changed.
        /// </summary>
        /// <param name="propertyName">The name of the property that changed.</param>
        protected void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

MappingDirection.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ComboBoxBindingIssue
{
    /// <summary>
    /// The mapping direction.
    /// </summary>
    public enum MappingDirection
    {
        None,
        Input,
        Output
    }
}

Mappings.cs:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;

namespace ComboBoxBindingIssue
{
    /// <summary>
    /// Represents a collection of mappings, as well as left and right element collections.
    /// </summary>
    public class Mappings
    {
        #region Properties

        /// <summary>
        /// The mapping collection.
        /// </summary>
        public BindingList<Mapping> Collection { get; private set; }

        /// <summary>
        /// The left element collection.
        /// </summary>
        /// <remarks>The collection of left elements is optional.</remarks>
        public BindingList<String> LeftElements { get; private set; }

        /// <summary>
        /// The right element collection.
        /// </summary>
        /// <remarks>The collection of right elements is optional.</remarks>
        public BindingList<String> RightElements { get; private set; }

        #endregion Properties

        /// <summary>
        /// Initializes a new instance of a Mappings class.
        /// </summary>
        public Mappings()
        {
            Collection = new BindingList<Mapping>();
            LeftElements = new BindingList<String>();
            RightElements = new BindingList<String>();
        }
    }
}

Program.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace ComboBoxBindingIssue
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            Mappings model = new Mappings();
            model.Collection.Add(new Mapping(String.Empty, "Column A"));
            model.Collection.Add(new Mapping(String.Empty, "Column B"));
            model.Collection.Add(new Mapping(String.Empty, "Column C"));
            model.Collection.Add(new Mapping(String.Empty, "Column D"));

            model.LeftElements.Add(String.Empty);
            model.LeftElements.Add("Column 1");
            model.LeftElements.Add("Column 2");
            model.LeftElements.Add("Column 3");
            model.LeftElements.Add("Column 4");
            model.LeftElements.Add("Column 5");

            MappingDialog dialog = new MappingDialog();
            dialog.Model = model;
            DialogResult result = dialog.ShowDialog();
        }
    }
}

Источник

Сообщение от nmcf

Как оно вообще у тебя возникает? Ты какие-то условия наложил на поля или что?

Ну, когда создавал БД в Аксесе, то задал полю Расстояние(км) тип Числовой. Теперь когда в DataGridView отображается таблица, я пытаюсь ввести в поле Расстояние текстовое значение, и он выдает окно с ошибкой. На скрине ведь видно всё.

Добавлено через 17 минут
Хочу просто стандартное окно с ошибкой заменить своим MessageBox’ом. Для этого нужно обработать событие DataError.. А вот как это сделать, не пойму.. Делаю вот так, но толку нет, всё равно всплывает стандартное оконо с ошибкой на полэкрана, что жутко некрасиво !

void dataGridView1_DataError(object sender, DataGridViewDataErrorEventArgs anError)
        {
            MessageBox.Show("Ошибка ввода !");
            anError.ThrowException = false;
        }

Добавлено через 1 час 17 минут
Смотрите, на одном из форумов увидел этот кусов кода. Может, он поможет решить данную проблему ? Я не совсем понимаю для чего нужна последняя строчка.

private void dg1_dataerror(object sender, DataGridViewDataErrorEventArgs e)
        {
           // Если ты сюда ни чего не вставишь, то при ошибочном значение, не произойдет ничего, кроме того что ты не
           // сможешь перейти в другую ячейку, до тех пор пока не введешь правильное значение.
           // Можешь поставить MessageBox (...) со своим сообщением.
        }
// Установка обработчика события:
            dataGridView1.DataError += new DataGridViewDataErrorEventHandler(dg1_dataerror);

Добавлено через 34 минуты
Наконец-то разобрался… !!!
Надо было этот делегат на разработчик запихнуть в Form_Load, и тогда наш обработчик события DataGridView1_DataError заработает.

public Form1()
        {
            InitializeComponent();
           dataGridView1.DataError += new DataGridViewDataErrorEventHandler(DataGridView1_DataError);
        }
 
        private void Form1_Load(object sender, EventArgs e)
        {
            // TODO: данная строка кода позволяет загрузить данные в таблицу "грузоперевозкиDataSet.Учёт_перевозок". При необходимости она может быть перемещена или удалена.
            this.учёт_перевозокTableAdapter.Fill(this.грузоперевозкиDataSet.Учёт_перевозок);
            // TODO: данная строка кода позволяет загрузить данные в таблицу "грузоперевозкиDataSet.Автомобили". При необходимости она может быть перемещена или удалена.
            this.автомобилиTableAdapter.Fill(this.грузоперевозкиDataSet.Автомобили);
            // TODO: данная строка кода позволяет загрузить данные в таблицу "грузоперевозкиDataSet.Водители". При необходимости она может быть перемещена или удалена.
            this.водителиTableAdapter.Fill(this.грузоперевозкиDataSet.Водители);
            // TODO: данная строка кода позволяет загрузить данные в таблицу "грузоперевозкиDataSet.Склад". При необходимости она может быть перемещена или удалена.
            this.складTableAdapter.Fill(this.грузоперевозкиDataSet.Склад);
            // TODO: данная строка кода позволяет загрузить данные в таблицу "грузоперевозкиDataSet.Пункты_назначения". При необходимости она может быть перемещена или удалена.
            this.пункты_назначенияTableAdapter.Fill(this.грузоперевозкиDataSet.Пункты_назначения);
 
        }
        public void DataGridView1_DataError(object sender, DataGridViewDataErrorEventArgs anError)
        {
            MessageBox.Show("Ошибка ввода!");
            anError.ThrowException = false;               
        }

Источник

DataGridView Default Error Dialog

—————————
The following exception occurred in the DataGridView:

System.ArgumentException: Parameter is not valid.
at System.Drawing.Image.FromStream(Stream stream, Boolean useEmbeddedColorManagement, Boolean validateImageData)
at System.Drawing.ImageConverter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value)
at System.Windows.Forms.Formatter.FormatObjectInternal(Object value, Type targetType, TypeConverter sourceConverter, TypeConverter targetConverter, String formatString, IFormatProvider formatInfo, Object formattedNullValue)
at System.Windows.Forms.Formatter.FormatObject(Object value, Type targetType, TypeConverter sourceConverter, TypeConverter targetConverter, String formatString, IFormatProvider formatInfo, Object formattedNullValue, Object dataSourceNullValue)
at System.Windows.Forms.DataGridViewCell.GetFormattedValue(Object value, Int32 rowIndex, DataGridViewCellStyle& cellStyle, TypeConverter valueTypeConverter, TypeConverter formattedValueTypeConverter, DataGridViewDataErrorContexts context)

To replace this default dialog please handle the DataError event.
—————————

Solution: I had my data in varbinary and trying to bind to the data grid.. Thats why problem occured. Modified the data into binary. This issue is resolved.

For more references:

http://social.msdn.microsoft.com/Forums/en/Vsexpressvb/thread/8e7dceaa-ce69-48dd-85e4-b6c6f5f03bd9

Источник

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