Please help i am trying to load data to my gridview

System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
Source=UNIFORMPROJVB
StackTrace: at UNIFORMPROJVB.Newsearchdata.OnRowDataBound(Object sender, GridViewRowEventArgs e) in C:\Users\Makumbi\source\repos\UNIFORMPROJVB\UNIFORMPROJVB\Forms\Newsearchdata.aspx.vb:line 80

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    'If e.Row.RowType = DataControlRowType.DataRow AndAlso Stockbooks.EditIndex = e.Row.RowIndex Then
    If (e.Row.RowType = DataControlRowType.DataRow) Then 
        'Find the DropDownList in the Row
        Dim ddlCountries As DropDownList = CType(e.Row.FindControl("ddlclasses"), DropDownList)
        ddlCountries.DataSource = GetData("SELECT DISTINCT(Class)as classr FROM Classes")
        ddlCountries.DataTextField = "Classr"
        ddlCountries.DataValueField = "Classr"
        ddlCountries.DataBind() 
        'Add Default Item in the DropDownList
        ddlCountries.Items.Insert(0, New ListItem("Please select"))
 
        'Select the Country of Customer in DropDownList
        Dim country As String = CType(e.Row.FindControl("Lblclasses"), Label).Text
        If country = "" Then
            Exit Sub
        Else 
            ddlCountries.Items.FindByValue(country).Selected = True
        End If
    End If
End Sub

Private Sub BindGrid()
    Dim cmd As New SqlCommand("SELECT Name,class as Classr,class,stream, House, ACNOS,admno,sex,STDTYPE,Autofield FROM STUDENT")
    Stockbooks.DataSource = Me.ExecuteQuery(cmd, "SELECT")
    Stockbooks.DataBind()
    Stockbooks.UseAccessibleHeader = True
    Stockbooks.HeaderRow.TableSection = TableRowSection.TableHeader
End Sub