Add row to datagrid

if(e.KeyChar == 13)
{
DataTable dtg = (DataTable) DataGrid1.DataSource;
DataRow dr = dtg.NewRow();
dr["Item_ID"]="ItemID";
dr["Item_Name"]="Item Name";
dr["Item_Desc"]="Item Description";
dr["Item_Amount"]="$15.65";
dtg.Rows.Add(dr);
DataGrid1.DataSource = dtg;
It will work for windows. 
If you use DataGrid in ASP then you will have to keep DataTable in Session:
DataTable dtg = new DataTable();
if (Session["SampleDataTable"]==null)
{

DataColumn dc;
dc = new DataColumn("Item_ID",System.Type.GetType("System.String"));
dtg.Columns.Add(dc);
dc = new DataColumn("Item_Name",System.Type.GetType("System.String"));
dtg.Columns.Add(dc);
dc = new DataColumn("Item_Desc",System.Type.GetType("System.String"));
dtg.Columns.Add(dc);
dc = new DataColumn("Item_Amount",System.Type.GetType("System.String"));
dtg.Columns.Add(dc);
}
else {dtg = (DataTable) Session["SampleDataTable"];}

DataRow dr = dtg.NewRow();
dr["Item_ID"]="ItemID";
dr["Item_Name"]="Item Name";
dr["Item_Desc"]="Item Description";
dr["Item_Amount"]="$15.35;
dtg.Rows.Add(dr);
DataGrid1.DataSource=dtg;
DataGrid1.PageSize+=1;
DataGrid1.DataBind();
Session["SampleDataTable"]=dtg;
}

Sample found from HERE[^]

Is it what you looking for ?

If you want the Grid to respond to Enter key in a custom way,then you have to create a new class that inherits from DataGrid & then override ProcessDialogKey and whenever the user presses Enter, call the method that adds row

This article will give you an idea on the inheriting part

Cheating the DataGridView[^]