Create README.md

README.md

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+# identitymodelbindingissue
+
+This application demonstrates the issue reported at: https://github.com/IdentityModel/IdentityModel2/issues/154    
+
+## Issue details
+
+Using IdentityServer4.AccessTokenValidation works perfectly fine with IdentityModel Version 3.9.0 but after upgrading to IdentityModel 3.10.1 the
+call to `AddIdentityServerAuthentication` in `Startup.cs` causes the following exception:
+
+```
+Could not load file or assembly 'IdentityModel, Version=3.6.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040).
+``` 
+
+* ASP.NET Core Web Application targeting .NET Framework 4.7.2 causes an exception due to a missing bindingredirect
+* AutoGenerateBindingRedirects is set to `true` and binding redirects are being created (after building the solution there is a `IdentityModelBindingIssue.exe.config` file in the `bin\debug\net472` folder
+that contains a lot of binding redirects)
+* IdentityServer4.AccessTokenValidation package depends on IdentityModel.AspNetCore.OAuth2Introspection which depends on IdentityModel 3.8.0
+* No binding redirect gets created for the transient dependency IdentityModel 3.8.0 (see commit 15f80e0e4a72b5653e6821372cb14f0081a49b5e)
+
+## Attempts to fix
+
+### Attempt 1
+
+* called `sn -T identitymodel.dll` to get the public key token: `e7877f4675df049f`
+* manually added a web.config file and specified a binding redirect for IdentityModel (see latest commit)
+
+#### Result
+
+* BindingRedirect from web config gets merged into automatically generated binding redirects in `IdentityModelBindingIssue.exe.config` but the problem remains
+
+### Attempt 2
+
+* disabled automatic binding redirects
+
+#### Results 1
+
+* started program, some other assembly-load-exceptions occured (as expected)
+* added a web.config and put all bindingredirects in there - they were ignored
+
+#### Results 2
+
+* removed web.config and added an app.config with bindingredirects 
+* app started up to the call to `AddIdentityServerAuthentication` and then the addembly load exception for the IdentityModel.dll reappeared
+
+