当返回的数据集包含一个空行时，Rows.Count = 1

Question

My query does not return anything but an empty row, since there is no records that meet all the criteria of my query. However, Rows.Count is 1 instead of 0. Here is my query:

SELECT LicenseID 
FROM LICENSES 
WHERE LicenseType = @LicenseType 
    AND DriverID = @DriverID 
    AND CarID IN(
        SELECT CarID 
        FROM CARS 
        WHERE CarSerial = @CarSerial 
            AND DriverID = @DriverID
    ) AND LicenseID IS NOT NULL 
    AND ((StartDate <= CONVERT(DATETIME, @EndDate)) 
    AND (EndDate >= CONVERT(DATETIME, @StartDate)))

Here is my C# if statement condition that for some reason keeps being true due to row count, even though there is no record meeting criteria:

if (ds != null && ds.Tables[0].Rows.Count > 0)

The database used is SQL Server. This previously seemed to work correctly under Oracle.

Answer 1

To Avoid ERROR:

if (ds.Tables.Count > 0)
 {
      if (ds.Tables[0].Rows.Count > 0)
      {
         //Then Return a value here or Get the date
                foreach (DataRow dr in ds.Tables[0].Rows)
                {
                    String getFirstRow = dr[0].ToString();
                    //And so on........
                }
      }
      else
      { 
            //Return value if no rows found.
      }
 }

Answer 2

what I needed to add was just an additional check for "LicenseID <> ''". "LicenseID IS NOT NULL" was not enough since there has been a record meeting all criteria but having LicenseID = "". I believe this has not been an issue with Oracle database, but turned out to be an issue after switching to SQL Server. Thanks for all your comments and suggestions.