Problem explained

The PowerBuilder project contains a .Net assembly that uses RestSharp to execute a GET call to the address https://www.google.de. When executing in PowerBuilder, the error message Could not load file or assembly ... appears. The problem is that PowerBuilder expects an assembly in a specific version. The assembly is available, but in a newer version. This can also be seen in pb-example-error.dll.config.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Runtime.CompilerServices.Unsafe" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Runtime.CompilerServices.Unsafe" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

Solution

When generating the DLLs, Costura Fody creates a single DLL, which means that all dependencies are self-contained and the error is corrected.

Example project

The sample project is located in Gitlab: https://github.com/tobiasoehler/PowerBuilder-DLL-Version-Problem-RestSharp