Suppose there is a Q# operation as follows:

operation Op () : Bool {

    let result = CSharpMethod ();
    return result

where CSharpMethod () is a defined method in the Driver class as follows:

public static bool CSharpMethod () {
    // ...
    // return a boolean value

So my question is how to call a method of a C# class inside a Q# operation and handle its returned value?



1 Answer 1


Q# operations are compiled into C# classes. To define a C# implementation for a Q# operation, you will need to do the following steps:

  1. Define a Q# operation with empty or intrinsic body CSharpMethod.
  2. Define a C# class that implements the abstract class into which your Q# operation gets compiled, something like public class CSharpMethod_Impl : CSharpMethod.
  3. Define method called Body in that class that does the actual computation that you need and returns the result.

This is a very hacky thing to do, so you might want to follow an example of operation GetOracleCallsCount and its C# implementation to see the exact pieces that have to be in place for it to work.

You can also see this question on StackOverflow that tries to do a similar thing.

  • $\begingroup$ Thanks for your time but my question is not about defining a C# implementation for a Q# operation, but it is about calling a C# method in the Q# operation. What I intend to do in this question is different from the purpose of the question to which you referred. $\endgroup$
    – Coder
    Jan 11, 2020 at 20:57
  • 1
    $\begingroup$ I understood that. There is no way to call a C# method from Q# directly without defining a Q# operation for it, so the approach I described is your best shot at getting it to work. $\endgroup$ Jan 12, 2020 at 1:32

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