error for new row and data sql

Question

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();