C# addRow and data, HELP!

Please help
I keep getting the following error: "Object reference not set to an instance of an object." for the code DataRow myRow = myTable.NewRow(); string connectionString = @"data source = GERHARDVDM28-PC; initial catalog = RacerUI; integrated security=SSPI";
string commandString = @"SELECT * FROM Entries";SqlDataAdapter dataAdapter = new SqlDataAdapter(commandString, connectionString);
SqlCommandBuilder scb = new SqlCommandBuilder(dataAdapter);DataSet racerUIDataSet = new DataSet();
DataTable myTable = racerUIDataSet.Tables["Entries"];this.entriesTableAdapter.Fill(this.racerUIDataSet.Entries);DataRow myRow = myTable.NewRow();
myRow[0] = RacerName;
myRow[1] = BikeManufacturer;
myRow[2] = RaceNumber;
myRow[3] = Team;
myTable.Rows.Add(myRow);
dataAdapter.Update(racerUIDataSet, "Entries");
racerUIDataSet.AcceptChanges();