ConnectionInfo connectionInfo = new CrystalDecisions.Shared.ConnectionInfo();
connectionInfo.ServerName = myDB;
connectionInfo.UserID = myUser;
connectionInfo.Password = myPassword;
 
// set report connection for main report
SetDBLogonForReport(connectionInfo, crReport, qServer);
// set report connection for any subreports
SetDBLogonForSubreports(connectionInfo, crReport, qServer);
---------------------
private void SetDBLogonForReport(ConnectionInfo connectionInfo, 
    ReportDocument reportDocument, string qServer)
{
  Tables tables = reportDocument.Database.Tables;
  foreach (CrystalDecisions.CrystalReports.Engine.Table table in tables)
  {
    TableLogOnInfo tableLogonInfo = table.LogOnInfo;
    tableLogonInfo.ConnectionInfo = connectionInfo;
    table.ApplyLogOnInfo(tableLogonInfo);
  }
}
---------------------
private void SetDBLogonForSubreports(ConnectionInfo connectionInfo, 
    ReportDocument reportDocument, string qServer)
{
  Sections sections = reportDocument.ReportDefinition.Sections;
  foreach (Section section in sections)
  {
    ReportObjects reportObjects = section.ReportObjects;
    foreach (ReportObject reportObject in reportObjects)
    {
      if (reportObject.Kind == ReportObjectKind.SubreportObject)
      {
        SubreportObject subreportObject = (SubreportObject)reportObject;
        ReportDocument subReportDocument =  
           subreportObject.OpenSubreport(subreportObject.SubreportName);
        SetDBLogonForReport(connectionInfo, subReportDocument, qServer);
      }
    }
  }
}