C# Error CS0582 – The ConditionalAttribute is not valid on an interface member

C# Compiler Error

CS0582 – The ConditionalAttribute is not valid on an interface member

Reason for the Error

You will get this error in your C# code when have used the conditional attribute on an interface member.

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

using System;
using System.Diagnostics;

namespace DeveloperPublishConsoleCore
{
    interface IEmployee
    {
        // CS0582  
        [ConditionalAttribute("ERROR")]  
        void GetEmployeeData();
    }

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

You will receive the error code CS0582 because you have an interface method GetEmployeeData and you have applied the ConditionalAttribute on it.

Error CS0582 The Conditional attribute is not valid on interface members DeveloperPublishConsoleCore C:\Users\senth\source\repos\DeveloperPublishConsoleCore\DeveloperPublishConsoleCore\Program.cs 9 Active

Solution

C# doesn’t allow you to have a condtional attribute on an interface member.

You can fix this error in your C# program by either removing the conditional attribute from the interface member.