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CommandField Constructor

  • Reference

Definition

Namespace:
System.Web.UI.WebControls
Assembly:
System.Web.dll

Initializes a new instance of the CommandField class.

public:
 CommandField();
public CommandField ();
Public Sub New ()

Examples

The following code example demonstrates how to use the constructor to dynamically add a CommandField field column to a GridView control.


<%@ Page language="C#" %>  

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  void Page_Load(Object sender, EventArgs e)
  {
    // Dynamically generated field columns need to be created only 
    // the first time the page is loaded.
    if (!IsPostBack)
    {
      // Create a CommandField object to display a Select button
      // for each record in the GridView control.
      CommandField selectCommandField = new CommandField();
      selectCommandField.ShowSelectButton = true;
      selectCommandField.SelectText = "Select Company"; 
      
      // Create a BoundField object to display the company names.
      BoundField lastNameBoundField = new BoundField();
      lastNameBoundField.DataField = "au_lname";
      lastNameBoundField.HeaderText = "Last Name";

      // Create a BoundField object to display a customer's company name.
      BoundField nameBoundField = new BoundField();
      nameBoundField.DataField = "CompanyName";
      nameBoundField.HeaderText = "Company Name";

      // Create a BoundField object to display a customer's city.
      BoundField cityBoundField = new BoundField();
      cityBoundField.DataField = "City";
      cityBoundField.HeaderText = "City";

      // Add the field columns to the ColumnFields collection of the
      // GridView control.
      CustomersGridView.Columns.Add(selectCommandField);
      CustomersGridView.Columns.Add(nameBoundField);
      CustomersGridView.Columns.Add(cityBoundField);
    }
  }

  void CustomersGridView_SelectedIndexChanged(Object sender, EventArgs e)
  {
    // Get the value of the company name and city from the appropriate cells.
    String companyName = CustomersGridView.SelectedRow.Cells[1].Text;
    String city = CustomersGridView.SelectedRow.Cells[2].Text;
   
    Message.Text = "You selected " + companyName + " located in " + city + ".";
  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>CommandField Constructor Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>CommandField Constructor Example</h3>

      <asp:label id="Message" 
        forecolor="Red"
        runat="server"/>

      <asp:gridview id="CustomersGridView" 
        datasourceid="CustomersSqlDataSource" 
        autogeneratecolumns="False"
        onselectedindexchanged="CustomersGridView_SelectedIndexChanged" 
        runat="server">                
      </asp:gridview>
            
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value   -->
      <!-- from the Web.config file.                            -->
      <asp:sqldatasource id="CustomersSqlDataSource"  
        selectcommand="Select [CustomerID], [CompanyName], [City] From [Customers]"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
        runat="server">
      </asp:sqldatasource>
            
    </form>
  </body>
</html>


<%@ Page language="VB" AutoEventWireup="False" %>  

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load

    ' Dynamically generated field columns need to be created only 
    ' the first time the page is loaded.
    If Not IsPostBack Then
    
      ' Create a CommandField object to display a Select button
      ' for each record in the GridView control.
      Dim selectCommandField As New CommandField()
      selectCommandField.ShowSelectButton = True
      selectCommandField.SelectText = "Select Company"
      
      ' Create a BoundField object to display the company names.
      Dim lastNameBoundField As New BoundField()
      lastNameBoundField.DataField = "au_lname"
      lastNameBoundField.HeaderText = "Last Name"

      ' Create a BoundField object to display a customer's company name.
      Dim nameBoundField As New BoundField()
      nameBoundField.DataField = "CompanyName"
      nameBoundField.HeaderText = "Company Name"

      ' Create a BoundField object to display a customer's city.
      Dim cityBoundField As New BoundField()
      cityBoundField.DataField = "City"
      cityBoundField.HeaderText = "City"

      ' Add the field columns to the ColumnFields collection of the
      ' GridView control.
      CustomersGridView.Columns.Add(selectCommandField)
      CustomersGridView.Columns.Add(nameBoundField)
      CustomersGridView.Columns.Add(cityBoundField)
      
    End If
      
  End Sub

  Sub CustomersGridView_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles CustomersGridView.SelectedIndexChanged
    
    ' Get the value of the company name and city from the appropriate cells.
    Dim companyName As String = CustomersGridView.SelectedRow.Cells(1).Text
    Dim city As String = CustomersGridView.SelectedRow.Cells(2).Text
   
    Message.Text = "You selected " & companyName & " located in " & city & "."
    
  End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>CommandField Constructor Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>CommandField Constructor Example</h3>

      <asp:label id="Message" 
        forecolor="Red"
        runat="server"/>

      <asp:gridview id="CustomersGridView" 
        datasourceid="CustomersSqlDataSource" 
        autogeneratecolumns="False"
        runat="server">                
      </asp:gridview>
            
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value   -->
      <!-- from the Web.config file.                            -->
      <asp:sqldatasource id="CustomersSqlDataSource"  
        selectcommand="Select [CustomerID], [CompanyName], [City] From [Customers]"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
        runat="server">
      </asp:sqldatasource>
            
    </form>
  </body>
</html>

Remarks

Use this constructor to initialize a new instance of the CommandField class. This constructor is commonly used when adding fields to a dynamically created data-bound control.

To dynamically add a CommandField field to a data-bound control, create a new CommandField object, set its properties, and then add it to the data-bound control's field collection. For example, if you are using the GridView control, add the CommandField object to the Columns collection.

Note

Although you can dynamically add fields to a data-bound control, it is strongly recommended that fields be statically declared and then shown or hidden, as appropriate. Statically declaring all your fields reduces the size of the view state for the parent data-bound control.

Applies to

See also