Please checkout the root cause and solution for below error message.

Error Message

An unhandled exception of type 'System.BadImageFormatException' occurred in SomeService.exe.

Additional information: Could not load file or assembly 'SomeAssembly, Version=1.0.0.XXXXX, Culture=neutral, PublicKeyToken=null' or one of its dependencies. An attempt was made to load a program with an incorrect format.

Problem (Root Cause)

It seems like you have taken the reference of any assembly whose target platform is x64 and your current project's target platform is x86 (32 bit) or vice versa.

Solution

To fix the issue, you have to make sure that your current project and the DLL your project is referencing, both should have the same target platform.