Description

When using Assembly.GetType(string, bool, bool) (in NET9) you can get unexpected FileLoadException depending on the input.

Depending on the passed in string parameter the method either succeeds (or fails) to look up a type, or throws an exception. Throwing that exception under those circumstances is certainly unexpected.

According to the documentation a FileLoadException will occur when

FileLoadException
name requires a dependent assembly that was found but could not be loaded.

alas - again according to the documentation,

This method only searches the current assembly instance

Specifically this occurs when using mscorlib as assembly to call things on. That assembly certainly should NOT have a problem "loading".

Reproduction Steps

Simple console program demonstrating the issue:

namespace Foo {
    internal class Program {
        static void Main(string[] args) {
            var mscorLibAssembly = typeof(string).Assembly;

            mscorLibAssembly.GetType("a,b", false, false);      // wont throw
            mscorLibAssembly.GetType("a,b,c", false, false);    // will throw
        }
    }
}

It seems, as soon as there are three (or more) , in the name parameter the method invocation throws.

Expected behavior

The method should certainly not throw a FileLoadException - because that indicates an issue with the probed assembly (here mscorlib) itself.

It might be reasonable to throw an ArgumentException because at least the docs state that this might occur

ArgumentException
name is invalid.

although "invalid" is not explained any further.

Preferably the method should not throw and just return null for a found type if the input is gibberish. Other runtimes - specifically NetFramework - simply returned null here.

Actual behavior

The method throws an unexpected exception FileLoadException on certain parameters.

Regression?

Yes. The method - and example code - will not throw an exception under previous versions of .NET (checked with .NET Framework 4.7.2 & .NET 8).

Known Workarounds

none

Configuration

NET 9.0.2

Other information

No response