Wpf – Why the WPF application has Drag & Drop disabled (even when AllowDrop is true)

DataGridView.SelectedCells is a collection of cells, so it's not as simple as calling ToString() on it. You have to loop through each cell in the collection and get each cell's value instead.

The following will create a comma-delimited list of all selected cells' values.

C#

TextBox1.Text = "";
bool FirstValue = true;
foreach(DataGridViewCell cell in DataGridView1.SelectedCells)
{
    if(!FirstValue)
    {
        TextBox1.Text += ", ";
    }
    TextBox1.Text += cell.Value.ToString();
    FirstValue = false;
}

VB.NET (Translated from the code above)

TextBox1.Text = ""
Dim FirstValue As Boolean =  True 
Dim cell As DataGridViewCell
For Each cell In DataGridView1.SelectedCells
    If Not FirstValue Then
        TextBox1.Text += ", "
    End If
    TextBox1.Text += cell.Value.ToString()
    FirstValue = False
Next

I've solved my problem I believe. I was running Visual Studio as Administrator. When it launched my application, it didn't recognize drags from Explorer because Explorer was running in User mode. Hope this bonehead move helps someone else out.