Set the Default Value of a FieldFilter on a Show Table Page

Normally, a Show Table page displays all records in a database table or view when the default value in the FieldFilter is set to "All". Sometimes you might want to display records specific to some value in a FieldFilter when the page is initially displayed. The sample code shown below sets the default value of a FieldFilter on a Show Table page and filters the data based on the default value set for the FieldFilter.

You can set the default value of a filter when a page loads the first time and filter the data based on the default value. Override the CreateWhereClause() method in the TableControl class and set the item selected in the FieldFilter. Then, override the PopulateTableFilter() method in the TableControl class to filter the page.

In the following example, the TableControl filters only rows whose CustomerID is "abc".

Step 2: Override the CreateWhereClause() and PopulateCustomerIDFilter() methods in the TableControl class.

For .NET Framework 1.1, add your code customization in the OrdersTableControl class of ShowOrdersTablePage.aspx.cs, located in

...\<Application Folder>\Orders\ShowOrdersTablePage.aspx.cs or .vb

For .NET Framework 2.0 and 3.0, add your code customization in the OrdersTableControl class of ShowOrdersTablePage.Controls.cs, located in

...\<Application Folder>\App_Code\Orders\ShowOrdersTablePage.Controls.cs or .vb

C#:

public override WhereClause CreateWhereClause() {     WhereClause wc = base.CreateWhereClause();     if ((wc == null))     {         wc = new WhereClause();     }     if (!this.Page.IsPostBack)     {         wc.iAND(OrdersTable.CustomerID, BaseFilter.ComparisonOperator.EqualsTo, "abc");     }     return wc; } protected override void PopulateCustomerIDFilter(string selectedValue, int maxItems) {     if (!this.Page.IsPostBack)         base.PopulateCustomerIDFilter("abc", maxItems);     else         base.PopulateCustomerIDFilter(selectedValue, maxItems); }

Visual Basic .NET:

Public Overrides Function CreateWhereClause() As WhereClause     Dim wc As WhereClause = MyBase.CreateWhereClause     if (wc Is Nothing) Then         wc = New WhereClause     End If     If Not Me.Page.IsPostBack Then         wc.iAND(OrdersTable.CustomerID, BaseFilter.ComparisonOperator.EqualsTo, “abc")     End If         Return wc End Function   Protected Overrides Sub PopulateCustomerIDFilter(ByVal selectedValue As String, ByVal maxItems As Integer)     If Not Me.Page.IsPostBack Then         MyBase.PopulateCustomerIDFilter("abc", maxItems)     Else         MyBase.PopulateCustomerIDFilter(selectedValue, maxItems)     End If End Sub

Step 3: Build and run your application.

Note: You can also use a URL parameter instead of a constant string to initialize a filter value. For example, if the URL parameter is called CustomerID, then you can

C#:

wc.iAND(OrdersTable.CustomerID, BaseFilter.ComparisonOperator.EqualsTo,         this.Page.Request.QueryString["CustomerID"]);

Visual Basic .NET:

wc.iAND(OrdersTable.CustomerID, BaseFilter.ComparisonOperator.EqualsTo, _         Me.Page.Request.QueryString(“CustomerID”))

Anh is a software engineer at Iron Speed, Inc. He enjoys developing applications with Iron Speed Designer and Microsoft .NET technology.