Well I wouldn't call that "ambiguous"! You have exceeded the amount of string literals that the compiler can handle and you need to reduce that.
Here are some ideas to help you do that:
If you are using the same text repeatedly (e.g. In error messages) then consider using Consts to minimize re-use of words unnecessarily - see
How to: Define Constants in C# | Microsoft Docs[
^]
Constants - C# Programming Guide | Microsoft Docs[
^]
Consider using a resource file to hold your string literals - see this CodeProject article
.NET String Resources[
^]
Or this one from MS -
Working with .resx Files Programmatically | Microsoft Docs[
^] (NB These articles refer to this as a great way of handling multiple languages - but it works when only one language is involved too!)
You refer to your project being "big" - you could try to break it down into multiple assemblies e.g.
Creating Satellite Assemblies for Desktop Apps | Microsoft Docs[
^] or class libraries - e.g. see
Creating C# Class Library (DLL) Using Visual Studio .NET[
^]
Without knowing anything about your style of coding, or being able to see any of your code I'm afraid we will struggle to help you much beyond this.
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