Comtrol in web form lost format after event gridview_romcommand

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VB

Gridview

Hi everyone!

I have a webform include gridview and some controls.
I merged cells in RowDatabound event:

Private Sub grvData_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles grvData.RowDataBound
       Try
           If e.Row.RowType = DataControlRowType.Header Then
               e.Row.Cells.RemoveAt(e.Row.Cells.Count - 1)
               e.Row.Cells(e.Row.Cells.Count - 1).ColumnSpan = 2
               e.Row.Cells(e.Row.Cells.Count - 1).Text = "Thao tác"
           End If
           If e.Row.RowType = DataControlRowType.Footer Then
               e.Row.Cells.RemoveAt(e.Row.Cells.Count - 1)
               e.Row.Cells.RemoveAt(e.Row.Cells.Count - 1)
               e.Row.Cells.RemoveAt(e.Row.Cells.Count - 1)
               e.Row.Cells(e.Row.Cells.Count - 1).ColumnSpan = 4
           End If
       Catch ex As Exception
           Throw New Exception(ex.Message, ex)
       End Try
   End Sub

The webform as below image:
01.jpg - Google Drive[^]

In the Gridview footer, when i click button "Thêm mới" to call event RowCommand of gridview:

Private Sub grvData_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles grvData.RowCommand
lblError.Text = String.Empty
Dim commandNameType As String = String.Empty
Try
    If e.CommandName = "Insert" Then
        commandNameType = "thêm"
        Dim txtName As TextBox = DirectCast(grvData.FooterRow.FindControl("txtNewName"), TextBox) 
        If String.IsNullOrEmpty(txtName.Text) Then
           Return
        End If
        lblError.text = "Đã tồn tại nguồn đơn . Bạn không thể tạo thêm được nguồn đơn này nữa"

        Return                   
    End If
Catch ex As Exception
    lblError.Text = "Lỗi không " & commandNameType & " được bản ghi này <br />" & ex.Message
End Try

And then, the Label lblError display text then my form lost format as below:
02.jpg - Google Drive[^]

How to keep format after click "Thêm mới" button?

What I have tried:

I tried use UpdatePanel but cannot solved.