In windows application, first of all you need to do is changing the DataGridView RowStyle so it can be auto sized based on your content
dataGridView1.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.Fill;
dataGridView1.RowsDefaultCellStyle.WrapMode = DataGridViewTriState.True;
then replace the comma by newline
Eval("test").ToString().Replace(",", System.Environment.NewLine);
Thanks
Sujeet