Generate warning on specific method call (.net binary class library)

Question

I am using some external .net libraries (already compiled, source code not available).

I would like to have some specific method calls to generate a compiler warning.

So for example, let's say we have the following class :

public class ExternalAPI
{
     public void MethodCallNotThreadSafe();
     public void MethodCallThreadSafe();
}

I would like that the following in my code generates a compiler warning (which will also trigger an error since using warning as errors, but that's off topic).

ExternalAPI api = new ExternalAPI();
api.MethodCallNotThreadSafe(); //Should trigger a warning

As mentioned, I do not have the source code for the library (or for some cases I do, but do not want to use obsolete), so Obsolete attribute is not an option.

Answer 1

You can use the Microsoft.CodeAnalysis.BannedApiAnalyzers NuGet package.

To summarize from its documentation, after adding the package to your project/solution, add a BannedSymbols.txt to your project/solution and this to your csproj(s)

<ItemGroup>
  <AdditionalFiles Include="path to BannedSymbols.txt"/>
</ItemGroup>

Now you just need to fill BannedSymbols.txt. One line should look like

{Documentation Comment ID string for the symbol}[;Description Text]

Given you're looking to get warnings for usage of a given method (ExternalAPI.MethodCallNotThreadSafe), the first part should look like M:Namespace.Type.Method which translates to M:ApiNamespace.ExternalAPI.MethodCallNotThreadSafe for you case. The second part is optional and lets you customize the warning's message.

For example with M:ApiNamespace.ExternalAPI.MethodCallNotThreadSafe; this method isn't thread safe, doing api.MethodCallNotThreadSafe(); will give you the following warning :

RS0030 : The symbol 'ExternalAPI.MethodCallNotThreadSafe()' is banned in this project: this method isn't thread safe.

Note that if the method you target has parameters nor type parameters, you'll have to adapt the first part accordingly to target the proper overload.