C# Error CS0577 – The Conditional attribute is not valid on ‘function’ because it is a constructor, destructor, operator, or explicit interface implementation

C# Compiler Error

CS0577 – The Conditional attribute is not valid on ‘function’ because it is a constructor, destructor, operator, or explicit interface implementation

Reason for the Error

You will get this error in your C# code when you have applied the conditional attributes to specific methods which are not supported by C#.

For example, let’s compile the below C# program

using System;
namespace DeveloperPublishConsole1
{
    interface IEmployee
    {
        void GetData();
    }
    public class MyClass : IEmployee
    {
        [System.Diagnostics.Conditional("a")]   // CS0577  
        void IEmployee.GetData()
        {

        }
    }
    internal class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}

You will receive the error code CS0577 because you have applied the conditional attribute on a method that is an explicit interface definition.

Error     CS0577 The Conditional attribute is not valid on ‘MyClass.IEmployee.GetData()’ because it is a constructor, destructor, operator, lambda expression, or explicit interface implementation               DeveloperPublishConsole1 C:\Users\SenthilBalu\source\repos\DeveloperPublishConsole1\DeveloperPublishConsole1\Program.cs               10          Active

Solution

C# doesn’t allow you to have an conditional attributes applied on a explicit interface definition.

You can fix this error in your C# program by removing the conditional attribute on the GetData() method in the class MyClass.