How to use a ComboBox control to edit data in a ListView control in Visual C# (320344)

SUMMARY

This step-by-step article demonstrates how to use a ComboBox control to edit the data in a ListView control. This method replaces the standard text box approach of editing the data in a ListView control

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Description of the Technique

By using the LabelEdit property of the ListView control, you can allow the user to edit the contents of the ListView control. To edit the data in the ListView control, you can use a standard text box. Occasionally, it is useful to have another control to edit the control. This article simulates how to use a ComboBox control to edit the data in a ListView when the ListView is in Details view.

When the user selects a row in the ListView, a calculation is performed to locate the bounding rectangle for the first column of the row that is clicked. That calculation takes into account that the column may not be visible or may not be fully visible when the row is clicked and when the ComboBox is sized and displayed appropriately.

In addition to positioning and sizing the ComboBox, this sample also watches for two messages on the ListView control: WM_VSCROLL and WM_HSCROLL. These messages occur whenever the user scrolls through the ListView control vertically or horizontally. Because the ComboBox is not physically part of the ListView control, the ComboBox does not automatically scroll with the ListView. Therefore, whenever either of these two messages occur, the ComboBox must be hidden. To watch for these messages, you create a custom UserControl class that inherits from the ListView class. In this custom control, the WndProc method is overridden to allow all messages to be checked for scrolling.

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Create the Inherited ListView Control

Start Microsoft Visual Studio .NET or Microsoft Visual Studio 2005.
On the File menu, point to New, and then click Project.
In the New Project dialog box, click Visual C# Projects under Project Types, and then click Windows Control Library under Templates.

Note In Visual Studio 2005, click Visual C# under Project Types.

Replace all of the code in the UserControl class with the following code:

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

namespace InheritedListView
{
   /// <summary>
   /// Summary description for UserControl1.
   /// </summary>
   public class MyListView : System.Windows.Forms.ListView
   {
      /// <summary>
      /// Required designer variable.
      /// </summary>
      private System.ComponentModel.Container components = null;

      public MyListView()
      {
         // This call is required by the Windows.Forms Form Designer.
         InitializeComponent();

         // TODO: Add any initialization after the InitForm call
      }

      /// <summary>
      /// Clean up any resources being used.
      /// </summary>
      protected override void Dispose( bool disposing )
      {
         if( disposing )
         {
            if( components != null )
               components.Dispose();
         }
         base.Dispose( disposing );
      }

      #region Component 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()
      {
         components = new System.ComponentModel.Container();
      }
      #endregion

      private const int WM_HSCROLL = 0x114;
      private const int WM_VSCROLL = 0x115;

      protected override void WndProc(ref Message msg)
      {
         // Look for the WM_VSCROLL or the WM_HSCROLL messages.
         if ((msg.Msg == WM_VSCROLL) || (msg.Msg == WM_HSCROLL))
         {
            // Move focus to the ListView to cause ComboBox to lose focus.
            this.Focus();  
         }

         // Pass message to default handler.
         base.WndProc(ref msg);
      } 
   }
}

Note The code should be changed in Visual Studio 2005. When you create a Windows Forms project, Visual C# adds one form to the project by default. This form is named Form1. The two files that represent the form are named Form1.cs and Form1.designer.cs. You write your code in Form1.cs. The Designer.cs file is where the Windows Forms Designer writes the code that implements all the actions that you performed by adding controls. For more information about the Windows Forms Designer in Visual C# 2005, visit the following Microsoft Web site:

http://msdn2.microsoft.com/en-us/library/ms173077.aspx

Save and build the project.

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Create the Sample Application

Follow these steps to create a new Windows Application in Visual C# .NET or in Visual C# 2005:
1. On the File menu, point to New, and then click Project.
2. In the New Project dialog box, click Visual C# Projects under Project Types, and then click Windows Application under Templates. By default, Form1 is created.
  
  Note In Visual Studio 2005, click Visual C# under Project Types.
Follow these steps to add the control that you created in the Create the Inherited ListView Control section to your Windows application:
1. On the Tools menu, click Customize Toolbox.
2. On the .NET Framework Components tab, click Browse.
3. In the Open dialog box, locate the control that you created in the Create the Inherited ListView Control section, and then click Open. This adds this control to the toolbox so that you can use the control similarly to any other control.
4. Drag MyListView from the General section of the toolbox to Form1.
Drag a ComboBox control from the Windows Forms section of the toolbox to Form1.
In the Properties window of ComboBox, change the Name property to cbListViewCombo, and then set the Visible property to False.
Add the following code to the class of Form1 above the constructor:
```
private ListViewItem lvItem;
					
```

Add the following code to the Load event of Form1:

// Add a few items to the combo box list.
this.cbListViewCombo.Items.Add("NC");
this.cbListViewCombo.Items.Add("WA");

// Set view of ListView to Details.
this.myListView1.View = View.Details;

// Turn on full row select.
this.myListView1.FullRowSelect = true;
			
// Add data to the ListView.
ColumnHeader columnheader;
ListViewItem listviewitem;

// Create sample ListView data.
listviewitem = new ListViewItem("NC");
listviewitem.SubItems.Add("North Carolina");
this.myListView1.Items.Add(listviewitem);

listviewitem = new ListViewItem("WA");
listviewitem.SubItems.Add("Washington");
this.myListView1.Items.Add(listviewitem);
            
// Create column headers for the data.
columnheader = new ColumnHeader();
columnheader.Text = "State Abbr.";
this.myListView1.Columns.Add(columnheader);

columnheader = new ColumnHeader();
columnheader.Text = "State";
this.myListView1.Columns.Add(columnheader);

// Loop through and size each column header to fit the column header text.
foreach (ColumnHeader ch in this.myListView1.Columns)
{			
   ch.Width = -2;
}

Add the following code to the SelectedValueChanged event of the ComboBox:

// Set text of ListView item to match the ComboBox.
lvItem.Text = this.cbListViewCombo.Text;
		
// Hide the ComboBox.
this.cbListViewCombo.Visible = false;

Add the following code to the Leave event of the ComboBox:

// Set text of ListView item to match the ComboBox.
lvItem.Text = this.cbListViewCombo.Text;

// Hide the ComboBox.
this.cbListViewCombo.Visible = false;

Add the following code to the KeyPress event of the ComboBox:

// Verify that the user presses ESC.
switch (e.KeyChar)
{
   case (char)(int)Keys.Escape:
   {
      // Reset the original text value, and then hide the ComboBox.
      this.cbListViewCombo.Text = lvItem.Text;
      this.cbListViewCombo.Visible = false;
      break;
   }

   case (char)(int)Keys.Enter:
   {		
      // Hide the ComboBox.
      this.cbListViewCombo.Visible = false;
      break;
   }
}

Add the following code to the MouseUp event of myListView1:

// Get the item on the row that is clicked.
lvItem = this.myListView1.GetItemAt(e.X, e.Y);

// Make sure that an item is clicked.
if (lvItem != null)
{
   // Get the bounds of the item that is clicked.
   Rectangle ClickedItem = lvItem.Bounds;

   // Verify that the column is completely scrolled off to the left.
   if ((ClickedItem.Left + this.myListView1.Columns[0].Width) < 0)
   {
      // If the cell is out of view to the left, do nothing.
      return;
   }

   // Verify that the column is partially scrolled off to the left.
   else if (ClickedItem.Left < 0)
   {
      // Determine if column extends beyond right side of ListView.
      if ((ClickedItem.Left + this.myListView1.Columns[0].Width) > this.myListView1.Width)
      {
         // Set width of column to match width of ListView.
         ClickedItem.Width = this.myListView1.Width;
         ClickedItem.X = 0;
      }
      else
      {
         // Right side of cell is in view.
         ClickedItem.Width = this.myListView1.Columns[0].Width + ClickedItem.Left;
         ClickedItem.X = 2;
      }					
   }
   else if (this.myListView1.Columns[0].Width > this.myListView1.Width)
   {
      ClickedItem.Width = this.myListView1.Width;
   }
   else
   {
      ClickedItem.Width = this.myListView1.Columns[0].Width;
      ClickedItem.X = 2;
   }				

   // Adjust the top to account for the location of the ListView.
   ClickedItem.Y += this.myListView1.Top;
   ClickedItem.X += this.myListView1.Left;	
				
   // Assign calculated bounds to the ComboBox.
   this.cbListViewCombo.Bounds = ClickedItem;
			
   // Set default text for ComboBox to match the item that is clicked.
   this.cbListViewCombo.Text = lvItem.Text;

   // Display the ComboBox, and make sure that it is on top with focus.
   this.cbListViewCombo.Visible = true;
   this.cbListViewCombo.BringToFront();
   this.cbListViewCombo.Focus();
}

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Verify That It Works

Save and run the sample.
Click a row in the ListView. Notice that a combo box appears over the location of the first column of the current row.
To hide the combo box, click an item in the combo box, press ESC, and then scroll through the ListView or click another control. Notice that the value that you clicked in the combo box is placed in the first column of the clicked row of the ListView.

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How to use a ComboBox control to edit data in a ListView control in Visual C# (320344)

IN THIS TASK

SUMMARY

Description of the Technique

Create the Inherited ListView Control

Create the Sample Application

Verify That It Works