Design Time:

 

1. Drag and drop a DataGrid on the form.
2. Set AllowSorting property of the grid to True.
3. Set AutogenerateColumns property of the grid to False.
4. Add bound columns to datagrid and set their properties as follows. The sortexpression property refers to the name of column in database table.

 

Note: Employees table from Northwind database is being used to illustrate the purpose.

 

DataTextField	Header Text	Sort Expression
EmployeeID	Employee ID	EmployeeID ASC
LastName	Last Name	LastName ASC
FirstName	First Name	FirstName ASC
Title	Title	Title ASC
City	City	City ASC
Country	Country	Country ASC

 

 

Run-time:

 

Pseudo logic:

 

1. Trap sortcommand event of the datagrid control.

 

2. Read sortexpression property of the event argument.

 

3. Sort data in grid using current sort expression.

 

4. Use split function to separate column name (which represents database field name) and sort direction. The first element of an array contains database field name.

 

5. If sort direction is ASC then new sort direction is DESC and vice versa. Save the new direction into 2^nd element of the array.

 

6. Loop through all columns

            If column’s sort expression matches sort expression returned from event argument then

                        Concatenate first element of an array, space and second element of an array to

build a new sort expression.

                        Assign new sort expression to current column’s sortexpression property.

                        Exit loop

            End If

End Loop

 

Note: In order for this example to work properly write binding SQL query with order by clause with no mention of column names. The column names are appended at run-time to the binding SQL query.

 

VB.Net Code:

 

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        'Put user code to initialize the page here

        If Not Page.IsPostBack Then

            BindDataGrid("EmployeeID ASC")

        End If

    End Sub

 

    Private Sub BindDataGrid(ByVal strSortField As String)

        Dim cn As SqlConnection

        Dim cmdSelect As SqlCommand

 

        cn = New SqlConnection("Server=localhost;UID=sa;PWD=;Database=Northwind")

        cmdSelect = New SqlCommand("Select * From employees Order By " & strSortField, cn)

        cn.Open()

        DataGrid1.DataSource = cmdSelect.ExecuteReader()

        DataGrid1.DataBind()

        cn.Close()

 

    End Sub

 

 

 

    Private Sub DataGrid1_SortCommand(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataGridSortCommandEventArgs) Handles DataGrid1.SortCommand

        Dim arrSortExpr() As String

        Dim i As Integer

 

        If e.SortExpression = "" Then Return

 

        BindDataGrid(e.SortExpression)

 

        arrSortExpr = Split(e.SortExpression, " ")

        For i = 0 To DataGrid1.Columns().Count - 1

            If (DataGrid1.Columns(i).SortExpression = e.SortExpression) Then

                If UCase(arrSortExpr(1)) = "ASC" Then

                    arrSortExpr(1) = "DESC"

                ElseIf UCase(arrSortExpr(1)) = "DESC" Then

                    arrSortExpr(1) = "ASC"

                End If

 

                DataGrid1.Columns(i).SortExpression = arrSortExpr(0) & " " & arrSortExpr(1)

                Exit For

            End If

        Next

    End Sub