You need to add a DataGridViewComboBoxColumn
to your dataGridView1
control and assign its DataSource
property to the collection of strings you want.
var myStringCollection = new[] {"String1", "String2", "String3"};
var comboColumn = new DataGridViewComboBoxColumn();
comboColumn.Name = "MyComboColumn";
comboColumn.DataSource = myStringCollection; //This sets the source of drop down items
Then insert it into your grid:
if (dataGridView1.Columns["MyComboColumn"] == null)
{
//The int value as first parameter of Insert() is the desired Column Index
dataGridView1.Columns.Insert(0, comboColumn);
}