add known issue BadImageFormatException (#1696)

* add known issue BadImageFormatException

* remove % from title

Documentation/KnownIssues.md

@@ -183,7 +183,7 @@ Stack Trace:
 
 *Solution:* Looks like this is caused by xUnit's app domains. For `dotnet test`, it can be disabled with the following argument: `-- RunConfiguration.DisableAppDomain=true`
 
-## Code coverage returns NaN%
+## Code coverage returns NaN
 
 *Symptoms:* You are getting following result when running Coverlet within CI/CD pipeline:
 
@@ -234,3 +234,18 @@ The XML code coverage report is too large for the coverlet to parse.
 *Potential Solutions:*
 
 * Reduce noise from auto generated code, for example excluding your EntityFrameworkCore Migrations namespace or automatically generated typed Http Clients. See [Excluding From Coverage](./MSBuildIntegration.md#excluding-from-coverage) for more information on ignoring namespaces from code coverage.
+
+## BadImageFormatException .NET Framework 4.7.x, 4.8.x
+
+*Symptoms:*
+
+```text
+BadImageFormatException during MetadataReaderProvider.FromPortablePdbStream in InstrumentationHelper.PortablePdbHasLocalSource, unable to check if the module has got local source.
+```
+
+*Solutions:*
+
+Change [DebugType](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-options/code-generation#debugtype) from `full` to `portable`.
+
+>[!IMPORTANT]
+>NET Core introduces a new symbol file (PDB) format - portable PDBs. Unlike traditional PDBs which are Windows-only, portable PDBs can be created and read on all platforms.

README.md

@@ -8,7 +8,7 @@
 |  coverlet.msbuild |  [![NuGet](https://img.shields.io/nuget/v/coverlet.msbuild.svg)](https://www.nuget.org/packages/coverlet.msbuild/)   |  [![NuGet](https://img.shields.io/nuget/dt/coverlet.msbuild.svg)](https://www.nuget.org/packages/coverlet.msbuild/) |
 |  coverlet.console |  [![NuGet](https://img.shields.io/nuget/v/coverlet.console.svg)](https://www.nuget.org/packages/coverlet.console/)     |  [![NuGet](https://img.shields.io/nuget/dt/coverlet.console.svg)](https://www.nuget.org/packages/coverlet.console/) |
 
-Coverlet is a cross platform code coverage framework for .NET, with support for line, branch and method coverage. It works with .NET Framework on Windows and .NET Core on all supported platforms.
+Coverlet is a cross platform code coverage framework for .NET, with support for line, branch and method coverage. It works with [.NET Framework](Documentation/KnownIssues.md#badimageformatexception-net-framework-47x-48x) on Windows and .NET Core on all supported platforms.
 
 **Coverlet documentation reflect the current repository state of the features, not the released ones.**
 **Check the [changelog](Documentation/Changelog.md) to understand if the documented feature you want to use has been officially released.**