VB.net (Win App) ติดปัญหาการแปลง Data Type จาก DataGridView ก่อนเก็บเข้า SQL SERVER ค่ะ

For i = 0 To DataGridView1.RowCount - 1

                Dim intRows As Integer
                sqlCheck = "SELECT COUNT(*) FROM TB_LOCATION WHERE LocNo = '" + DataGridView1.Rows(i).Cells(1).Value + "'"
                cmd = New SqlCommand(sqlCheck, con)
                intRows = cmd.ExecuteScalar()

                If intRows > 0 Then

                    LisFindUp = True
                    cmd.CommandText = "UPDATE TB_LOCATION SET " & " LocType = '" & CStr(DataGridView1.Rows(i).Cells(3).Value) & "', LocPlace = '" & CStr(DataGridView1.Rows(i).Cells(4).Value) & "' WHERE LocNo = '" & DataGridView1.Rows(i).Cells(1).Value & "'"
                    cmd.ExecuteNonQuery()

                Else

                    IsFindAdd = True
                    SqlIns2 = "INSERT INTO TB_LOCATION (LocNo,LocType,LocPlace) VALUES(@LocNo,@LocType,@Place)"
                    cmd = New System.Data.SqlClient.SqlCommand(SqlIns2, con)
                    cmd.Parameters.Add(New SqlParameter("@LocNo", DataGridView1.Rows(i).Cells(1).Value))
                    cmd.Parameters.Add(New SqlParameter("@LocType", DataGridView1.Rows(i).Cells(3).Value))
                    cmd.Parameters.Add(New SqlParameter("@Place", DataGridView1.Rows(i).Cells(4).Value))
                    cmd.ExecuteNonQuery()

                End If

                Dim intRows2 As Integer
                sqlCheck = "SELECT COUNT(*) FROM TB_INVENTORY WHERE PartNo = '" + DataGridView1.Rows(i).Cells(0).Value + "' AND LocNo = '" + DataGridView1.Rows(i).Cells(1).Value + "'"
                cmd = New SqlCommand(sqlCheck, con)
                intRows2 = cmd.ExecuteScalar()


                If intRows2 > 0 Then

                    LisFindUp = True
                    cmd.CommandText = "UPDATE TB_INVENTORY SET " & " Instock = '" & CDec(DataGridView1.Rows(i).Cells(2).Value) & "' WHERE PartNo = '" + DataGridView1.Rows(i).Cells(0).Value + "' AND LocNo = '" + DataGridView1.Rows(i).Cells(1).Value + "'"
                    cmd.ExecuteNonQuery()

                Else

                    IsFindAdd = True
                    SqlIns = "INSERT INTO TB_INVENTORY (PartNo,LocNo,Instock) VALUES(@PartNo,@LocNo,@Instock)"
                    cmd = New System.Data.SqlClient.SqlCommand(SqlIns, con)
                    cmd.Parameters.Add(New SqlParameter("@PartNo", DataGridView1.Rows(i).Cells(0).Value))
                    cmd.Parameters.Add(New SqlParameter("@LocNo", DataGridView1.Rows(i).Cells(1).Value))
                    cmd.Parameters.Add(New SqlParameter("@Instock", DataGridView1.Rows(i).Cells(2).Value))
                    cmd.ExecuteNonQuery()

                End If
            Next

SqlIns2 = "INSERT INTO TB_LOCATION (LocNo,LocType,LocPlace) VALUES(@LocNo,@LocType,@Place)"
                    cmd = New System.Data.SqlClient.SqlCommand(SqlIns2, con)
                    cmd.Parameters.Add(New SqlParameter("@LocNo", SqlDbType.VarChar = DataGridView1.Rows(i).Cells(1).Value))
                    cmd.Parameters.Add(New SqlParameter("@LocType", SqlDbType.VarChar = DataGridView1.Rows(i).Cells(3).Value))
                    cmd.Parameters.Add(New SqlParameter("@Place", SqlDbType.VarChar = DataGridView1.Rows(i).Cells(4).Value))
                    cmd.ExecuteNonQuery()

SqlIns = "INSERT INTO TB_INVENTORY (PartNo,LocNo,Instock) VALUES(@PartNo,@LocNo,@Instock)"
                    cmd = New System.Data.SqlClient.SqlCommand(SqlIns, con)
                    cmd.Parameters.Add(New SqlParameter("@PartNo", SqlDbType.VarChar = DataGridView1.Rows(i).Cells(0).Value))
                    cmd.Parameters.Add(New SqlParameter("@LocNo", SqlDbType.VarChar = DataGridView1.Rows(i).Cells(1).Value))
                    cmd.Parameters.Add(New SqlParameter("@Instock", SqlDbType.Decimal = DataGridView1.Rows(i).Cells(2).Value))
                    cmd.ExecuteNonQuery()