Slow performance of Reporting Services, very fast in QueryAnalyser

BTW, you don't need to use Profiler to see the generated SQL.

var query = ( from c in db.Customers where c.LastName = "Someone" select c );

// output the query SQL Debug.WriteLine(query);

Return query.ToList();

Alternatively, what we did was to hook into DataContext's Log property. This writes out our SQL and parameters automatically everytime we hit the database. We have found this very useful to identify unnecessary database calls.

public class DataBase : DataBaseModelDataContext
{
    internal DataBase()
    {
    }

    public DataBase(CommonObjects.BaseParameters param) {
        #If (DEBUG) 
        Log = new DataBaseLoger();
        #endIf //(DEBUG) 
    }

    public override void SubmitChanges(System.Data.Linq.ConflictMode failureMode)
    {   
        System.Data.Linq.ChangeSet cs = GetChangeSet();

        // update audit fields for each insert
        foreach (object entity in cs.Inserts)
        {
            UpdateAuditFields(entity);                               
        }

        // update audit fields for each update
        foreach (object entity in cs.Updates)
        {
            UpdateAuditFields(entity);
        }

        base.SubmitChanges(failureMode);
    }
}

public class DataBaseLoger : System.IO.TextWriter { public override Encoding Encoding { get { return new System.Text.UTF8Encoding(); } }

    public override void WriteLine(string value)
    {
        System.Diagnostics.Trace.WriteLine(System.DateTime.Now.ToString("hh:mm:ss") + " " + value, "Information");
    }

    public override void WriteLine()
    {
        System.Diagnostics.Trace.WriteLine("", "Information");            
    }

    public override void WriteLine(string format, params object[] arg)
    {
        WriteLine(string.Format(format, arg));
    }
}

Not the way you are describing it.

Reporting services needs a report definition to generate the report (the .rdlc). It can't just guess. You can create the definition programmatically. After all, the .rdlc is just XML in the form of the report definition language schema.

You could loop through the result set, creating new report table columns for each column in the result set or something like that. I've never tried this, but I think it will be damn near impossible to get reliable formatting if the columns, sizes, etc are not known ahead of time. I don't know how many different queries you are talking about, but the effort to do something like this may not be worth it.

Are these queries radically different? Do they return the same basic type of data?