在嵌套的For循环中获取DataGridView单元格值

Question

I've got some data displayed on a DataGridView , and in my btnSave_Click event, I'm calling a subroutine to validate the data in the grid before saving it into my database.

The way I'm doing it is by using a loop for each row and inside that loop using another for loop, for each column.

I need to then compare each char in the cell value that it's validating (row dr, cell dc). However, I cannot work out the way to use the row/column co-ordinates to get the value in the cell.

It's a little hard to explain what I mean, but in this code I have the For Loops set up on the first 2 lines, then on the third line, notice If IsDBNull(dc.TextInCell) - TextInCell is what I need to replace.

In Row; dr and Column; dc, I need to then validate the value stored in that cell...

For Each dr As DataGridViewRow In dgvImport.Rows
   For Each dc As DataGridViewColumn In dgvImport.Columns
     If dc.HeaderText = "Product Code" Then
       If IsDBNull(dc.TextInCell) = True Or dc.TextInCell = Nothing Or dc.TextInCell = "" Then
          Me.Cursor = Cursors.Default
          MsgBox("Import failed. One or more required fields were not entered", MsgBoxStyle.OkOnly, "Error")
          Exit Sub
        End If
        For Each c As Char In dc.TextInCell
         If Not Char.IsLetterOrDigit(c) Then
          If Not Char.IsWhiteSpace(c) Then
           If c <> "&" AndAlso c <> "-" AndAlso c <> "(" AndAlso c <> ")" Then
             Me.Cursor = Cursors.Default
             MsgBox("Import failed. One or more cells contains an invalid character", MsgBoxStyle.OkOnly, "Error")
             Exit Sub
           End If
          End If
         End If
Next

How do I get the cell value into a variable from here to send it through the validation?

Answer 1

It will (almost) always be faster to iterate the rows in the datatable than to root thru the control. There is also at least one inefficiency in your code:

For Each dr As DataGridViewRow In dgvImport.Rows
    For Each dc As DataGridViewColumn In dgvImport.Columns
        If dc.HeaderText = "Product Code" Then

You dont need to find the target column for each row - it will be at the same index for each row.

I dont know what the expected pattern is for these, but if there is a defined pattern like "N-LLL-AAA-NLN" (eg: 9-WDM-6K6-6ZC ) you might want to look into RegEx for comprehensive pattern testing. For instance your code is basically just testing for a limited set of special characters anywhere in the string; if there is a ( shouldn't it be before any ) ?

You will surely need to fiddle with the actual validation code, but this is many times faster:

'... code to fill the DT
' add a column to track if the row is valid
dtSample.Columns.Add(New DataColumn("IsValid", GetType(Boolean)))

Dim specialChars = "&-()"
Dim txt As String = ""
Dim bValid As Boolean
Dim prodIndex As Int32

' index of the target column using the column name
prodIndex = dtSample.Columns.IndexOf("ProductCode")  

For Each dr As DataRow In dtProduct.Rows
    ' get the text
    txt = dr.Field(Of String)(prodIndex)

    ' first check for nothing from DBNull
    bValid = String.IsNullOrEmpty(txt) = False
    ' if there is text data, check the content
    If bValid Then
        ' each char must be letter, digit or authorized special char
        For n As Int32 = 0 To txt.Length - 1
            If Char.IsLetterOrDigit(txt(n)) = False AndAlso
                        specialChars.Contains(txt(n)) = False Then
                bValid = False
                Exit For
            End If
        Next
    End If
    ' unabiguously set the column for each row
    dr("IsValid") = bValid
Next

dgv1.DataSource = dtSample
' hide our scratch column
dgv1.Columns("IsValid").Visible = False

Results:

Not shown is 2-3 lines in the RowPrePaint event to color the rows where IsValid is false. More importantly, it is fast: 125 milliseconds to process 75,000 rows; digging thru the DGV and finding the same column over and over takes 7-8 secs.

Even without RegEx, you can test for special characters at specific locations (assuming a fixed pattern). For instance, to test "A-78*X(2012)" :

bValid = pcode(1) = "-"c AndAlso
         pcode(4) = "*"c AndAlso
         pcode(6) = "("c AndAlso
         pcode(11) = ")"c

You could also split the string by those characters in order to test that parts(3) is a value between 2010 and 2015 or whatever, if you wanted to perform that level of testing. The more of that you do, the more useful RegEX would be.