What is the maximum number of parameters that a C# method can be defined as taking?

I am trying to figure out what the maximum number of parameters a method in C# can have. I’ve checked everywhere for an answer, including the C# official documentation, MSDN, and a couple of CLR references and I can’t find an answer. Does anyone have an answer to this question?

Answer

Here is your theoretical answer:

In order to push method arguments onto the stack, compiled code has the following MSIL opcodes to choose from:

ldarg.0

ldarg.1

ldarg.2

ldarg.3

ldarg.S

ldarg

ldarg.0 to ldarg.3 is used to push the first 4 method arguments onto the stack (including this as the first argument for instance methods).

ldarg.S takes an 8-bit argument number, and so it can be used to push up to 256 arguments onto the stack.

That leaves us with plain old ldarg, which can handle the most method arguments: it takes an unsigned 16-bit argument number, so the largest number of arguments that can be successfully compiled into valid MSIL is 2^16 = 65,536.

As others have noted, however, the actual limit will depend on implementation details of the runtime. Based on rmiesen’s answer, it looks like the current .NET implementation limits the maximum number of parameters to 2^14.

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