SSRS - Set Credentials Programmatically

Hi,

I need to set the datasource credentials when calling a SSRS report. I get this error:

rsCredentialsNotSpecified400One or more data source credentials required to run the report have not been specified.

Here is my code to date. What do I have to update here to pass correct credentials?

ReportService2005.ReportingService2005 rs = new ReportService2005.ReportingService2005();
ReportExecution2005.ReportExecutionService rsExec = new ReportExecution2005.ReportExecutionService();

// Authenticate to the Web service using Windows credentials
rs.Credentials = System.Net.CredentialCache.DefaultCredentials;
rsExec.Credentials = System.Net.CredentialCache.DefaultCredentials;

// Assign the URL of the Web service
rs.Url = string.Format("http://{0}/ReportServer/ReportService2005.asmx", SSRSBuilder.URL);
rsExec.Url = string.Format("http://{0}/ReportServer/ReportExecution2005.asmx", SSRSBuilder.URL);

Thanks!