view crystal report based on combobox selection

You can use pass dataset to report doc :

// code to get data from the DB
DBConnection DBConn = new DBConnection();
OleDbDataAdapter myDataAdapter = DBConn.getDataFromDB();

// use the created Dataset to fill it with data got
// from the DB by using the DataAdapter
DataSet dataReport = new DataSet();
myDataAdapter.Fill(dataReport,"myPersonalInfoTable");
// create a new report from the created CrystalReport
myDataReport myDataReport = new myDataReport();

// set the data source of the report
myDataReport.SetDataSource(dataReport);

// set the report source of the created “crystalReportViewer”
// component to the created report
crystalReportViewer1.ReportSource = myDataReport;