C#: multiline text in DataGridView control

You should set DefaultCellStyle.WrapMode property of column to DataGridViewTriState.True. After that text in cells will be displayed correctly.

Example (DataGridView with one column):

dataGridView1.Columns[0].DefaultCellStyle.WrapMode = DataGridViewTriState.True;
dataGridView1.Rows.Add("test" + Environment.NewLine + "test");

(Environment.NewLine = \r\n in Windows)