Hello there.

I have created a custom control derived from TextBox and want to bind a Property to a BindingSource on my Form. The Problem is if the Current of the BindingSource changes (by changing the current row of the grid - without changing data in the TextBox), the ListChanged Event on my underlying DataSource is also raised (setting my DataSource to be modified). This does only happen when I bind my created Property (even though it's just bridging the original Text). When I bind the Text property of the TextBox the event is not raised.

What am I missing here?

Example:

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

namespace BindingSourceTest
{
public partial class Form1 : Form
{
DataTable dt = null;
BindingSource s = null;
public Form1()
{
InitializeComponent();


//Add some data to our datasource
dt = new DataTable("table");
dt.Columns.Add("text");
dt.Columns.Add("value");

for (int i = 0; i < 10; i++)
dt.Rows.Add("Text " + i.ToString(), i.ToString());

dt.AcceptChanges();
dt.RowChanged += new DataRowChangeEventHandler(dt_RowChanged);

//Create a bindingsource for our datasource
s = new BindingSource(dt, "");
dataGridView1.DataSource = s;

//if Text is bound the ListChanged is not raised
myTextBox1.DataBindings.Add("MyText", s, "value");
}

void dt_RowChanged(object sender, DataRowChangeEventArgs e)
{
MessageBox.Show("Changes detected");
}


}

partial class Form1
{
/// <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.Column1 = new System.Windows.Forms.DataGridViewTextBoxColumn();
this.Column2 = new System.Windows.Forms.DataGridViewTextBoxColumn();
this.myTextBox1 = new BindingSourceTest.MyTextBox();
((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit();
this.SuspendLayout();
//
// dataGridView1
//
this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
this.dataGridView1.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {
this.Column1,
this.Column2});
this.dataGridView1.Location = new System.Drawing.Point(12, 12);
this.dataGridView1.Name = "dataGridView1";
this.dataGridView1.RowTemplate.Height = 24;
this.dataGridView1.Size = new System.Drawing.Size(255, 308);
this.dataGridView1.TabIndex = 0;
//
// Column1
//
this.Column1.DataPropertyName = "text";
this.Column1.HeaderText = "Column1";
this.Column1.Name = "Column1";
//
// Column2
//
this.Column2.DataPropertyName = "value";
this.Column2.HeaderText = "Column2";
this.Column2.Name = "Column2";
//
// myTextBox1
//
this.myTextBox1.Location = new System.Drawing.Point(27, 337);
this.myTextBox1.Name = "myTextBox1";
this.myTextBox1.Size = new System.Drawing.Size(240, 22);
this.myTextBox1.TabIndex = 1;
//
// Form1
//
this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 16F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(284, 413);
this.Controls.Add(this.myTextBox1);
this.Controls.Add(this.dataGridView1);
this.Name = "Form1";
this.Text = "Form1";
((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit();
this.ResumeLayout(false);
this.PerformLayout();

}

#endregion

private System.Windows.Forms.DataGridView dataGridView1;
private System.Windows.Forms.DataGridViewTextBoxColumn Column1;
private System.Windows.Forms.DataGridViewTextBoxColumn Column2;
private MyTextBox myTextBox1;

}

public class MyTextBox : System.Windows.Forms.TextBox
{
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public string MyText
{
get
{
return base.Text;
}
set
{
base.Text = value;
}
}

}
}

You can suppressedListChanged event from firingby setting the RaiseListChangedEvents property to false

Suppressing the event is not quite what i want - I need the event to be raised if the contents of the list change, but if the property i bind has no change - the event should not be raised, as i does with the standard Text property of the TextBox