Making GridView Clickable

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VB

ASP.NET

I'd be glad if someone could kindly modify the following code so that GridView becomes click-able. The problem is that the code in question works perfectly in my Windows application under CellMouseClick Event of DataGridView but it doesn't work in the Web application since there's no such event therein. So, under what event can it be made click-able?

Try
        dr = Nothing
        Dim str As String
        str = GridView1.SelectedValue(0).Value
        cmd = New SqlCommand("Select* from ProgramDetails.Subjects where SubjectCode='" & str & "'", cn)
        dr = cmd.ExecuteReader
        While (dr.Read)
            txtIdNumber.Text = dr(0)
            txtSubjectCode.Text = dr(1)
            txtSubjectName.Text = dr(2)
            If dr(3) = "Core" Then
                rbnCore.Checked = True
            Else
                rbnElective.Checked = True
            End If
            txtUserId.Text = dr(4)
            txtPassword.Text = dr(5)
        End While
        dr.Close()
        btnSave.Enabled = False
    Catch ex As Exception
    End Try