Populating a DataGridView with different value types?

[Using VB 2010 / Winforms / targeting .NET 2.0]

Hey guys,

Been working on a project that contains a DataGridView, and just got a bit hung up on part of it. The DGV is unbound and is not connected to any database or anything... I am simply populating it on form load by using StreamReader to grab the data from a local CSV file. Like so...

Code:

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  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        ' Read data from CSV file and populate DGV with it
        Dim fileName As String = Application.StartupPath & "\Data.csv"
        Dim TextLine As String = ""
        Dim SplitLine() As String
        If System.IO.File.Exists(fileName) = True Then
            Dim objReader As New System.IO.StreamReader(fileName)
            Do While objReader.Peek() <> -1
                TextLine = objReader.ReadLine()
                SplitLine = Split(TextLine, ",")
                DataGridView1.Rows.Add(SplitLine)
            Loop
            objReader.Dispose()
        Else
            MsgBox("CSV file not found.")
        End If

    End Sub

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The DGV has 3 columns. Let's say they are named "FoodName", "FoodType", and "FoodImage". The "FoodName" and "FoodType" columns will hold text data, and the "FoodImage" column will hold images (these images will be stored in My.Resources).

So, the contents of the CSV file might look something like this...

Apple, Fruit, AppleImage
Broccoli, Veggie, BroccoliImage
Cantaloup, Fruit, CantaloupImage

So what I can't figure out is .... when the rows are being added to the DGV during form load... when it gets to a cell that is (ultimately) supposed to hold an image, I need it to change that cell's value type from "text" to "image", and then populate that cell with the correct image from My.Resources.

Here's how I've tried to accomplish that during the DGV "rows added" event (which fires as each row is being added as the stream reader is reading the CSV file). FYI, I know that the commented lines below don't work, but it should give you an ideas as to what I'm trying to do...

Code:

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  Private Sub DataGridView1_RowsAdded(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewRowsAddedEventArgs) Handles DataGridView1.RowsAdded

        For Each Row As DataGridViewRow In DataGridView1.Rows
            For Each Cell As DataGridViewCell In Row.Cells
                If Cell.Value = "AppleImage" Then
                    Cell.ValueType = Image ' Change the cell value type from 'Text' to 'Image'
                    Cell.Value = My.Resources.AppleImage ' Populate the cell with the correct image
                ElseIf Cell.Value = "BroccoliImage" Then
                    Cell.ValueType = Image ' Change the cell value type from 'Text' to 'Image'
                    Cell.Value = My.Resources.BroccoliImage ' Populate the cell with the correct image
                ElseIf Cell.Value = "CantaloupImage" Then
                    Cell.ValueType = Image ' Change the cell value type from 'Text' to 'Image'
                    Cell.Value = My.Resources.CantaloupImage ' Populate the cell with the correct image
                End If
            Next
        Next

    End Sub

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FYI, the user will be able to add new data to the cells in the DGV. Then, on form close, the data from the DGV will be written to the CSV file (so I will need to convert each "image" cell back to its "text" representation so that I can store it all in the CSV file). Here's the sub I'm using to do that, which I call during the 'form closing' event...

Code:

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  Public Sub SaveDataToFile(ByRef fileName As String)

        Dim I As Integer = 0
        Dim j As Integer = 0
        Dim cellvalue$
        Dim rowLine As String = ""

        Try

            Dim objWriter As New System.IO.StreamWriter(fileName, False)
            For j = 0 To (DataGridView1.Rows.Count - 1)
                For I = 0 To (DataGridView1.Columns.Count - 1)
                    If Not TypeOf DataGridView1.CurrentRow.Cells.Item(I).Value Is DBNull Then
                        If Not TypeOf DataGridView1.CurrentRow.Cells.Item(I).Value Is Image Then
                            cellvalue = DataGridView1.Item(I, j).Value
                        Else
                            cellvalue = DataGridView1.Item(I, j).Tag
                        End If
                    Else
                        cellvalue = ""
                    End If
                    rowLine = rowLine + cellvalue + ","
                Next
                objWriter.WriteLine(rowLine)
                rowLine = ""
            Next
            objWriter.Close()
            objWriter.Dispose()
            Application.DoEvents()

        Catch e As Exception

            MessageBox.Show("An error occured while writing to the CSV file." + e.ToString())

        Finally

            FileClose(1)

        End Try

    End Sub

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Hopefully what I'm trying to do makes sense. The code that writes to the CSV file ("SaveDataToFile" sub) seems to work fine. But I just can't figure out how to get the "DataGridView1_RowsAdded" sub to work (specifically, how to convert the text representation of an image to the actual image within the cell). Can anyone tell me what I need to change to make this work? Or am I way off base with my code, and need to do something entirely different?

Sorry for the length of this post, but it's as short as I could make it to explain everything correctly.

Thanks!

Quote:

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when it gets to a cell that is (ultimately) supposed to hold an image, I need it to change that cell's value type from "text" to "image", and then populate that cell with the correct image from My.Resources.

---

Or you could just add a DataGridViewImageColumn for which the cell.Value property is always of the type Image.

Quote:

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Originally Posted by dunfiddlin

Or you could just add a DataGridViewImageColumn for which the cell.Value property is always of the type Image.

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I already tried that, but I get an exception when I do that ("invalid cast from 'System.String' to 'System.Drawing.Image"), because the StreamReader in the form load code is populating the DGV one row at a time.

In other words, I don't know how to populate a DGV programmatically (from a CSV file) if each DGV column is a different value type.

Do you know how to do this? I've searched online for a solution for this for a few hours, but haven't found one yet. I'd greatly appreciate a quick example, if anyone knows how this is done! :)

It's simple enough. Instead of just whacking everything in with .... DataGridView1.Rows.Add(SplitLine) ... add the cell values one at a time on a for loop and when the column with the image comes up do your 'if string is so and so thiscell.Value = therightimage' there and then. If you leave it til after the row is complete you're well and truly scuppered!

I would do you it in code but it's 2.15am, I've just got back from walking the dogs, and bed seems like an awfully good idea! Must ... stop ... being distracted by forum! :afrog: