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PODataGridView repeatedly recreating columns
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  1. PODataGridView repeatedly recreating columns
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    copied!<p>I have a problem when assigning the <code>DataSource</code> propery on a <code>DataGridView</code> control. My <code>DataSource</code> is a <code>DataTable</code>'s <code>DefaultView</code> and, as expected, columns are automatically created in the <code>DataGridView</code> to match those in the <code>DataTable</code> when I assign it.</p> <p>What happens next is that the columns seem to be automatically removed and recreated a further 2 times by the <code>DataGridView</code>. Why would this happen?</p> <p>In a form's constructor:</p> <pre><code>//A DataTable is created with 5 columns //The DataTable is populated with some rows. myDgv.AutoGenerateColumns = true; myDgv.DataSource = myDataTable.DefaultView; // myDgv.ColumnAdded event is fired 5 times. // WHY: myDgv.ColumnRemoved event is fired 5 times. // WHY: myDgv.ColumnAdded event is fired 5 times. // WHY: myDgv.ColumnRemoved event is fired 5 times. // WHY: myDgv.ColumnAdded event is fired 5 times. </code></pre> <hr> <p><strong>Edit: Added a (hopefully) self contained example. If I set breakpoints in the event handlers, I hit the 'Added' one 6 times and the 'Removed' one 4 times. The DataTable contains 2 columns and I never ask for any columns to be removed in my code.</strong></p> <pre><code>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 asdasdgf { public class Form1 : Form { public Form1() { InitializeComponent(); DataTable dt = new DataTable(); dt.Columns.Add("Col1", typeof(int)); dt.Columns.Add("Col2", typeof(string)); foreach (int i in Enumerable.Range(0, 10)) { var row = dt.NewRow(); row["Col1"] = i; row["Col2"] = "stackoverflow"; dt.Rows.Add(row); } dataGridView1.ColumnAdded += new DataGridViewColumnEventHandler(dataGridView1_ColumnAdded); dataGridView1.ColumnRemoved += new DataGridViewColumnEventHandler(dataGridView1_ColumnRemoved); dataGridView1.DataSource = dt.DefaultView; } void dataGridView1_ColumnRemoved(object sender, DataGridViewColumnEventArgs e) { // Break here } void dataGridView1_ColumnAdded(object sender, DataGridViewColumnEventArgs e) { // Break here } // Form1.Designer.cs contents: #region Windows Form Designer generated code private System.ComponentModel.IContainer components = null; private System.Windows.Forms.DataGridView dataGridView1; protected override void Dispose(bool disposing) { if (disposing &amp;&amp; (components != null)) { components.Dispose(); } base.Dispose(disposing); } /// &lt;summary&gt; /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// &lt;/summary&gt; private void InitializeComponent() { this.dataGridView1 = new System.Windows.Forms.DataGridView(); ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit(); this.SuspendLayout(); // // dataGridView1 // this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize; this.dataGridView1.Location = new System.Drawing.Point(12, 41); this.dataGridView1.Name = "dataGridView1"; this.dataGridView1.Size = new System.Drawing.Size(240, 150); this.dataGridView1.TabIndex = 0; // // Form1 // this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F); this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font; this.ClientSize = new System.Drawing.Size(284, 264); this.Controls.Add(this.dataGridView1); this.Name = "Form1"; this.Text = "Form1"; ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit(); this.ResumeLayout(false); } #endregion } } </code></pre>
 

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