Dependency Injection error: Unable to resolve service for

I created an .NET Core MVC application and use Dependency Injection and Repository Pattern to inject a repository to my controller. However, I am getting an error:

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EfCategoryDal:

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GenericRepository

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CategoryManager
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ICategoryService
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CategoryController
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Startup
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I’m not sure what I’m doing wrong. Any ideas?

Thanks

>Solution :

startup.cs

services.AddDbContext<Context>();