GridView.SortExpression Property (System.Web.UI.WebControls)

SortExpression Property

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

GridView..::.SortExpression Property

Updated: November 2007

Gets the sort expression associated with the column or columns being sorted.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in System.Web.dll)

Syntax

Visual Basic (Declaration)

<BrowsableAttribute(False)> _
Public Overridable ReadOnly Property SortExpression As String

Visual Basic (Usage)

Dim instance As GridView
Dim value As String

value = instance.SortExpression

[BrowsableAttribute(false)]
public virtual string SortExpression { get; }

Visual C++

[BrowsableAttribute(false)]
public:
virtual property String^ SortExpression {
    String^ get ();
}

/** @property */
/** @attribute BrowsableAttribute(false) */
public String get_SortExpression()

JScript

public function get SortExpression () : String

Property Value

Type: System..::.String

The sort expression associated with the column or columns being sorted.

Remarks

Use the SortExpression property to determine the sort expression associated with the column or columns being sorted.

Note:
The GridView control has a built-in sorting feature that automatically sets this property. This property is typically used only when you need to programmatically determine the column or columns being sorted or when you are adding your own custom sorting functionality to a GridView control.

When multiple columns are sorted, this property contains a comma-separated list of the fields by which to sort.

Examples

The following example demonstrates how to use the SortExpression property to determine the name of the column being sorted.

Visual Basic

<%@ Page language="VB" %>

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

  Sub CustomersGridView_RowCreated(ByVal sender As Object, ByVal e As GridViewRowEventArgs)

    ' Use the RowType property to determine whether the 
    ' row being created is the header row. 
    If e.Row.RowType = DataControlRowType.Header Then

      ' Call the GetSortColumnIndex helper method to determine
      ' the index of the column being sorted.
      Dim sortColumnIndex As Integer = GetSortColumnIndex()

      If sortColumnIndex <> -1 Then

        ' Call the AddSortImage helper method to add
        ' a sort direction image to the appropriate
        ' column header. 
        AddSortImage(sortColumnIndex, e.Row)

      End If

    End If

  End Sub

  ' This is a helper method used to determine the index of the
  ' column being sorted. If no column is being sorted, -1 is returned.
  Function GetSortColumnIndex() As Integer

    ' Iterate through the Columns collection to determine the index
    ' of the column being sorted.
    Dim field As DataControlField
    For Each field In CustomersGridView.Columns

      If field.SortExpression = CustomersGridView.SortExpression Then

        Return CustomersGridView.Columns.IndexOf(field)

      End If

    Next

    Return -1

  End Function

  ' This is a helper method used to add a sort direction
  ' image to the header of the column being sorted.
  Sub AddSortImage(ByVal columnIndex As Integer, ByVal row As GridViewRow)

    ' Create the sorting image based on the sort direction.
    Dim sortImage As New Image()
    If CustomersGridView.SortDirection = SortDirection.Ascending Then

      sortImage.ImageUrl = "~/Images/Ascending.jpg"
      sortImage.AlternateText = "Ascending Order"

    Else

      sortImage.ImageUrl = "~/Images/Descending.jpg"
      sortImage.AlternateText = "Descending Order"

    End If
    ' Add the image to the appropriate header cell.
    row.Cells(columnIndex).Controls.Add(sortImage)

  End Sub

</script>

<html  >
  <head runat="server">
    <title>GridView AllowSorting Example</title>
</head>
<body>
    <form id="form1" runat="server">

      <h3>GridView AllowSorting Example</h3>

      <asp:gridview id="CustomersGridView" 
        datasourceid="CustomersSource" 
        autogeneratecolumns="false"
        emptydatatext="No data available." 
        allowsorting="true"
        onrowcreated="CustomersGridView_RowCreated"
        runat="server">

        <columns>
          <asp:boundfield datafield="CustomerID"
            headertext="Customer ID"
            headerstyle-wrap="false" 
            sortexpression="CustomerID"/>
          <asp:boundfield datafield="CompanyName"
            headertext="CompanyName"
            headerstyle-wrap="false"
            sortexpression="CompanyName"/>
          <asp:boundfield datafield="Address"
            headertext="Address"
            headerstyle-wrap="false"
            sortexpression="Address"/>
          <asp:boundfield datafield="City"
            headertext="City"
            headerstyle-wrap="false"
            sortexpression="City"/>
          <asp:boundfield datafield="PostalCode"
            headertext="Postal Code"
            headerstyle-wrap="false"
            sortexpression="PostalCode" />
          <asp:boundfield datafield="Country"
            headertext="Country"
            headerstyle-wrap="false"
            sortexpression="Country"/>         
        </columns>

      </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="CustomersSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country] From [Customers]"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>

    </form>
  </body>
</html>

<%@ 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 CustomersGridView_RowCreated(Object sender, GridViewRowEventArgs e)
  {

    // Use the RowType property to determine whether the 
    // row being created is the header row. 
    if (e.Row.RowType == DataControlRowType.Header)
    {
      // Call the GetSortColumnIndex helper method to determine
      // the index of the column being sorted.
      int sortColumnIndex = GetSortColumnIndex();

      if (sortColumnIndex != -1)
      {
        // Call the AddSortImage helper method to add
        // a sort direction image to the appropriate
        // column header. 
        AddSortImage(sortColumnIndex, e.Row);
      }
    }
  }

  // This is a helper method used to determine the index of the
  // column being sorted. If no column is being sorted, -1 is returned.
  int GetSortColumnIndex()
  {

    // Iterate through the Columns collection to determine the index
    // of the column being sorted.
    foreach (DataControlField field in CustomersGridView.Columns)
    {
      if (field.SortExpression == CustomersGridView.SortExpression)
      {
        return CustomersGridView.Columns.IndexOf(field);
      }
    }

    return -1;
  }

  // This is a helper method used to add a sort direction
  // image to the header of the column being sorted.
  void AddSortImage(int columnIndex, GridViewRow headerRow)
  {

    // Create the sorting image based on the sort direction.
    Image sortImage = new Image();
    if (CustomersGridView.SortDirection == SortDirection.Ascending)
    {
      sortImage.ImageUrl = "~/Images/Ascending.jpg";
      sortImage.AlternateText = "Ascending Order";
    }
    else
    {
      sortImage.ImageUrl = "~/Images/Descending.jpg";
      sortImage.AlternateText = "Descending Order";
    }

    // Add the image to the appropriate header cell.
    headerRow.Cells[columnIndex].Controls.Add(sortImage);

  }

</script>

<html  >
  <head runat="server">
    <title>GridView AllowSorting Example</title>
</head>
<body>
    <form id="form1" runat="server">

      <h3>GridView AllowSorting Example</h3>

      <asp:gridview id="CustomersGridView" 
        datasourceid="CustomersSource" 
        autogeneratecolumns="false"
        emptydatatext="No data available." 
        allowsorting="true"
        onrowcreated="CustomersGridView_RowCreated"
        runat="server">

        <columns>
          <asp:boundfield datafield="CustomerID"
            headertext="Customer ID"
            headerstyle-wrap="false" 
            sortexpression="CustomerID"/>
          <asp:boundfield datafield="CompanyName"
            headertext="CompanyName"
            headerstyle-wrap="false"
            sortexpression="CompanyName"/>
          <asp:boundfield datafield="Address"
            headertext="Address"
            headerstyle-wrap="false"
            sortexpression="Address"/>
          <asp:boundfield datafield="City"
            headertext="City"
            headerstyle-wrap="false"
            sortexpression="City"/>
          <asp:boundfield datafield="PostalCode"
            headertext="Postal Code"
            headerstyle-wrap="false"
            sortexpression="PostalCode" />
          <asp:boundfield datafield="Country"
            headertext="Country"
            headerstyle-wrap="false"
            sortexpression="Country"/>         
        </columns>

      </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="CustomersSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country] From [Customers]"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>

    </form>
  </body>
</html>

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information