How to create multi-column primary key for a DataTable in C#
To create a primary key from multiple columns in DataTable you can create a new DataColumn and pass the columns as array in constructor.Example
DataTable dt = new DataTable();
dt.TableName = "Orders";
DataColumn dc1 = new DataColumn();
dc1.ColumnName = "Order Id";
dc1.DataType = typeof(int);
dt.Columns.Add(dc1);
DataColumn dc2 = new DataColumn();
dc2.ColumnName = "ClientName";
dc2.DataType = typeof(string);
dt.Columns.Add(dc2);
dt.PrimaryKey = new DataColumn[] { dc1,dc2 }; //Creating primary key here