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How to Resolve Warning "CS0612: 'member' is obsolete" in C#

The Compiler Warning CS0612 is a deprecation warning. The message reads: "'Member' is obsolete".

This warning occurs when you use a class, method, property, or field that has been marked with the [Obsolete] attribute. The author of that code (whether it's Microsoft, a third-party library, or your own team) is signaling that this specific member should no longer be used. While the code will still compile and run correctly for now, the member is likely unstable, inefficient, or scheduled for removal in future versions.

This guide explains how to handle deprecated code properly.

Understanding the [Obsolete] Attribute​

Developers mark code as obsolete to manage the lifecycle of an API.

  • Refactoring: A better method name or signature exists.
  • Safety: The old method has flaws or security risks.
  • Cleanup: The feature is being phased out.

When you see CS0612, it means the attribute was applied like this: [Obsolete]. If the attribute includes a specific message (e.g., [Obsolete("Use NewMethod")]), you will usually see CS0618 instead, but the principle is identical.

Scenario: Using a Deprecated Method​

This warning triggers simply by calling the member.

Definition​

public class LegacyService
{
    // The library author marked this as Obsolete
    [Obsolete] 
    public void OldSave()
    {
        Console.WriteLine("Saving the old way...");
    }

    public void NewSave()
    {
        Console.WriteLine("Saving the new way!");
    }
}

Usage with Warning​

public class Program
{
    static void Main()
    {
        var service = new LegacyService();

        // ⛔️ Warning CS0612: 'LegacyService.OldSave()' is obsolete
        service.OldSave(); 
    }
}

The intended resolution for this warning is to stop using the old member. Check the documentation or IntelliSense metadata for the obsolete member; it often suggests the replacement.

Solution: switch to the non-obsolete alternative.

public class Program
{
    static void Main()
    {
        var service = new LegacyService();

        // ✅ Correct: Using the modern API
        service.NewSave(); 
    }
}

Solution 2: Suppress the Warning (Temporary)​

If you are maintaining a legacy system and cannot update the code yet (or if the library has provided no alternative), you can suppress the warning to clean up your build log.

Using Pragma​

Wrap the specific call in pragma directives.

public class Program
{
    static void Main()
    {
        var service = new LegacyService();

        // ✅ Correct: Warning suppressed for this specific line only
        #pragma warning disable CS0612
        service.OldSave();
        #pragma warning restore CS0612
    }
}
warning

Do not ignore indefinitely: Suppressing the warning does not fix the underlying issue. The method might be removed entirely in the next version of the library, causing your build to break (Error CS0619).

Conclusion​

CS0612 is a "heads up" from the library author.

  1. Investigate: Look at the method definition. Is there a newer version?
  2. Refactor: Replace the call with the current best practice.
  3. Suppress: Only if you are strictly maintaining legacy behavior and cannot upgrade.

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