[.Net]Error ตรง "Object reference not set to an instance of an object." ครับ ต้องแก้ยังไงดีครับ

    Private Sub txtSearch_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles txtSearch.KeyDown
        If txtSearch.Text <> "" Then
            If (e.KeyCode = Keys.Enter) Then

                Dim sqlPrintColor As String = ""
                sqlPrintColor = "SELECT * FROM PrintColor"

                If cboSearch.SelectedIndex = 0 Then
                    sqlPrintColor &= " WHERE (PrintCLID='" & txtSearch.Text & "')"
                ElseIf cboSearch.SelectedIndex = 1 Then
                    sqlPrintColor &= " WHERE (ColorName LIKE '%" & txtSearch.Text & "%')"

                End If

                sqlPrintColor &= " ORDER BY PrintCLID"

                With Conn
                    If .State = ConnectionState.Open Then
                        .Close()
                        .ConnectionString = strConn
                        .Open()
                    End If
                End With

                If IsFind = True Then
                    ds.Tables("PrintColor").Clear()
                End If

                da.SelectCommand.CommandText = sqlPrintColor
                da.Fill(ds, "PrintColor")

                If ds.Tables("PrintColor").Rows.Count <> 0 Then
                    IsFind = True

                    ClearAllBinding()

                    txtPrintCLID.DataBindings.Add("Text", ds, "PrintColor.PrintCLID")
                    txtColorName.DataBindings.Add("Text", ds, "PrintColor.ColorName")


                    txtColorInShop.DataBindings.Add("Text", ds, "PrintColor.ColorInShop")
                    txtColorInDisclose.DataBindings.Add("Text", ds, "PrintColor.ColorInDisclose")
                    txtColorTotal.DataBindings.Add("Text", ds, "PrintColor.ColorTotal")

                    dt = ds.Tables("PrintColor")

                    ShowPosition()

                    cmdAdd.Enabled = False
                    cmdEdit.Enabled = True

                    cmdMoveFirst.Enabled = True
                    cmdMovePrevious.Enabled = True
                    cmdMoveNext.Enabled = True
                    cmdMoveLast.Enabled = True

                    cmdEdit.Focus()
                Else
                    IsFind = False
                    MessageBox.Show("อุปกรณ์ที่คุณระบุ ไม่มี !!!", "ผลการตรวจสอบ", MessageBoxButtons.OK, MessageBoxIcon.Information)

                    ClearData()

                    lblShowPositions.Text = ""

                    cmdAdd.Enabled = True
                    cmdEdit.Enabled = False

                    cmdMoveFirst.Enabled = False
                    cmdMovePrevious.Enabled = False
                    cmdMoveNext.Enabled = False
                    cmdMoveLast.Enabled = False

                    txtSearch.Focus()
                    txtSearch.SelectAll()
                    Exit Sub
                End If
            End If
        End If
    End Sub