system.argumentexception:DataGridViewcombobox cell value is not valid

Do you have the combobox in the 1st column ?
Try to change to :

For Each row As DataGridViewRow In Me.DataGridView1.Rows
        If not row.IsNewRow Then
            Dim CTRcell As DataGridViewComboBoxCell = DirectCast(row.Cells(0), DataGridViewComboBoxCell)
            CTRcell.Value = centeridandname
        End If
  Next

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Sorry wrong answer :(
The problem is not the new row, for that message, but the assing of the value. If you want to select one value you can do this way:

        For Each row As DataGridViewRow In Me.DataGridView1.Rows
            If Not row.IsNewRow Then
                row.Cells(0).Value = "1"
            End If
        Next
 
        ' Where "1" is the name of the item to select 

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Hi Ipaulino,I was waiting for you, Thanks for your reply, i tried the above code...but  "row.IsNewRow" is returning true....if i commented the if not row is new row line, it is returning the same exception "system.argumentexception:DataGridViewcombobox cell value is not valid."

Check my second comment :)
I have understood wrongly your problem.

heer is the code i have

For Each row As DataGridViewRow In Me.DataGridView1.Rows
           
             
                row.Cells(0).Value =centeridandname
         
        Next

in this case it is returning the same exception....

when i tried


 For Each row As DataGridViewRow In Me.DataGridView1.Rows
            If Not row.IsNewRow Then
             
                row.Cells(0).Value = ObjTA.centeridandname
            End If
        Next


The execution is not going to the row.cell(0).value line because, the "row.isnewrow" is returning true...

What is centeridandname variable ? You must specify a valid STRING that are in the itens of the combobox
You could try
row.Cells(0).Value =centeridandname.ToString()

Ok, it's a new row then remove that line.

nope! that is not working out!.. it is returning the same error

Can you show a picture of what you have ?
centeridandname is a string variable and exists in the datagridviewcombobox ?

the canterid and name is returning "0000-abc" , which exists in the combobox dataset...

k ipaulo, thanks a lot, Give a min, i l chek on this....

i have this right now

For Each row As DataGridViewRow In Me.DataGridView1.Rows
         
            row.Cells(0).Value = ObjTA.centeridandname.ToString()
           
        Next

 Private Sub DataGridView1_DataError(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewDataErrorEventArgs) Handles DataGridView1.DataError
        If e.Context = DataGridViewDataErrorContexts.Formatting Or e.Context = DataGridViewDataErrorContexts.PreferredSize Then
            e.ThrowException = False
        End If
    End Sub



the error message is handled....But it is looping in the datagridview1_error event ...and still not displaying the value in the selected combobox...

Once again please CHECK if the values is available in the datasource and if the COLUMN is the index 0 (1st column)
Here's an working example if you want to try:

Public Class Form1
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
        ' Creates a datatable
        Dim dt As New DataTable
        dt.Columns.Add("id", GetType(Integer)).AutoIncrement = True
        dt.Columns.Add("item", GetType(String))
 
        ' Adds some values
        For x As Int16 = 0 To 10
            Dim dr As DataRow = dt.NewRow
            dr("item") = "Item " & x.ToString
            dt.Rows.Add(dr)
        Next
 
        ' Create a new combo and adds it to the grid
        Dim combo As New DataGridViewComboBoxColumn
        combo.DataSource = dt.DefaultView
        combo.DisplayMember = "item"
        combo.ValueMember = "id"
 
        Me.DataGridView1.Columns.Add(combo)
 
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        For Each row As DataGridViewRow In Me.DataGridView1.Rows
            row.Cells(0).Value = "Item 3"
        Next
    End Sub
 
    Private Sub DataGridView1_DataError(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewDataErrorEventArgs) Handles DataGridView1.DataError
        If e.Context = DataGridViewDataErrorContexts.Formatting Or e.Context = DataGridViewDataErrorContexts.PreferredSize Then
            e.ThrowException = False
        End If
    End Sub
 
End Class

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Thanks a lot ipaulino...I really hard tough time with this datagridview, Which very few of them are familiar with, U Helped me in many instances.....

Glad I could help!
jpaulino