CS0103 — The name does not exist in the current context

Environment: C# compiler (Roslyn), during compilation.

What the diagnostic actually says

The compiler cannot resolve an identifier at the point where it is used. Most often, the name is misspelled, capitalization differs, or a local variable was declared inside a block whose scope already ended. Importing a namespace will not repair a missing local variable. Check the line and column in the compiler output before changing imports.

Reproduce: scope, not missing package

using System;
class Program {
    static void Main() {
        if (true) { int attempts = 3; }
        Console.WriteLine(attempts); // CS0103: attempts is out of scope
    }
}

Move the declaration into the enclosing method and then assign within the conditional:

using System;
class Program {
    static void Main() {
        int attempts = 0;
        if (true) { attempts = 3; }
        Console.WriteLine(attempts);
    }
}

Expected output: 3. With the first version, dotnet build should report CS0103 if these sources belong to a valid C# project; in the second, the identifier is in scope and definitely assigned.

Investigation path

1. Compare spelling and capitalization with the declaration. Attempt and attempt are different names.
2. Look for closing braces between the declaration and the use. A local declared in if, for, or a helper method cannot be used outside that scope.
3. If you intended to access an instance field, make sure you are inside the appropriate instance context and use this.field where helpful; a static method cannot directly access a nonstatic field.
4. For generated source or conditional compilation, verify the expected declaration is present in this build configuration.
5. Rebuild the specific project showing the error. Inspect the first diagnostic rather than fixing secondary cascades.

Boundary test and mistake to avoid

Try changing attempts to Attempts in just the print statement and observe the failure again. Do not make the variable global merely to silence CS0103: choose the smallest correct scope, and pass values as parameters when crossing method boundaries.