9 Answers, 1 is accepted

SN

Like so:
'QX', 'AA', 'EF'
Something like that.
Currently the expression editor does not support list of values. But you can do that in the report constructor right after InitializeComponent like this:
this.ReportParameters["MyReportParameter"].Value = new string[] { "QX", "AA", "EF" };
Greetings,
Steve
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Please check the updated help article regarding multivalue report parameters - Using Multivalue Parameters.
Regards,
Stef
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Please check the Specifying Default Values for a MultiValue Parameter section of Using MultiValue parameters.
You can use the Array built-in function to specify multiple initially selected values. The listed values must be available in the ValueMember fields of the parameter.
Regards,
Stef
Telerik by Progress

I still can't preview the report doing this though. If I try to set design-time parameters using "Array" it says something along the lines of "undefined function reference Array". So what you're suggesting works when the report is opened in the browser, which at that point I'll just pass those parameters myself since I'm using the HTML5 viewer.
Also, I ended up just using an object data source and passing the parameters in from the client side (JavaScript), as Object parameters. Then I convert them to the appropriate types (List<int>) and call the stored proc.
This was necessary anyways as the parameters have to be sent to the proc as a user-defined Table type.
Multivalue parameters are evaluated as arrays of object, and require additional handling in the SQL query to be turned into a custom variable.
In addition to the found by you approach, you can use a stored procedure in which values are read, turned into a Table-valued parameter that is passed to another stored procedure.
Regards,
Stef
Telerik by Progress