ErrorListProvider Project Name not show

private void initErrorListProvider() 
{
    _errors = new List<ErrorTask>(); 
    ServiceProvider serviceProvider = new ServiceProvider((Microsoft.VisualStudio.OLE.Interop.IServiceProvider)_applicationObject.DTE); 
    _errorListProvider = new Microsoft.VisualStudio.Shell.ErrorListProvider(serviceProvider); 
    _errorListProvider.ProviderName = "My Error Provider"; 
    _errorListProvider.ProviderGuid = new Guid("8550EB61-847D-4d1e-A3AB-582262BD6AAE"); 
    _errorListProvider.Show();
}
private void addError(Project project, String file, TaskErrorCategory category, int line, int column, String text) 
{
    ErrorTask errorTask = new ErrorTask(); 
    errorTask.ErrorCategory = category;
    // Visual Studio uses indexes starting at 0  
    // while the automation model uses indexes starting at 1
    errorTask.Line = line - 1;
    errorTask.Column = column - 1;
    errorTask.Navigate +=
    new EventHandler(errorTaskNavigate); 
    errorTask.Document = file;
    errorTask.Category =
    TaskCategory.BuildCompile; 
    errorTask.Text = text;
    _errors.Add(errorTask);
    _errorListProvider.Tasks.Add(errorTask);
}