How to get columns Primary key constraints using SqlConnection.GetSchema()

I have some code of ADO.NET to dynamically detect the database schema, what I need is how to get unique columns constraints and Primary key constraints using the GetSchema method on SqlConnection. This is the code that I have:

conn.Open();     
SqlCommand mSqlCommand = new SqlCommand("sp_pkeys", conn);
mSqlCommand.CommandType = CommandType.StoredProcedure;
mSqlCommand.Parameters.Add(
    "@table_name", SqlDbType.NVarChar).Value = tableName;
SqlDataReader mReader = mSqlCommand.ExecuteReader(
    (CommandBehavior.KeyInfo | CommandBehavior.SchemaOnly));
//ExecuteReader();
DataTable schema = mReader.GetSchemaTable();
mReader.Close();
conn.Close();