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.

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

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.