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Compiler Error CS0116

  • Article

A namespace cannot directly contain members such as fields or methods.

A namespace can contain other namespaces, structs, and classes. For more information, see the namespace keyword article.

Example

The following sample will cause Visual Studio to flag parts of the code as being in violation of CS0116. Attempting to build this code will result in build failure:

// CS0116.cs
namespace x
{
    // A namespace can be placed within another namespace.
    using System;

    // These variables trigger the CS0116 error as they are declared outside of a struct or class.
    public int latitude;
    public int longitude;
    Coordinate coord;

    // Auto-properties also fall under the definition of this rule.
    public string LocationName { get; set; }

    // This method as well: if it isn't in a class or a struct, it's violating CS0116.
    public void DisplayLatitude()
    {
        Console.WriteLine($"Lat: {latitude}");
    }

    public struct Coordinate
    {
    }

    public class CoordinatePrinter
    {
        public void DisplayLongitude()
        {
            Console.WriteLine($"Longitude: {longitude}");
        }

        public void DisplayLocation()
        {
            Console.WriteLine($"Location: {LocationName}");
        }
    }
}

Note that in C#, methods and variables must be declared and defined within a struct or class. For more information on program structure in C#, see the General Structure of a C# Program article. To fix this error, rewrite your code such that all methods and fields are contained within either a struct or a class:

namespace x
{
    // A namespace can be placed within another namespace.
    using System;

    // These variables are now placed within a struct, so CS0116 is no longer violated.
    public struct Coordinate
    {
        public int Latitude;
        public int Longitude;
    }

    // The methods and fields are now placed within a class, and the compiler is satisfied.
    public class CoordinatePrinter
    {
        Coordinate coord;
        public string LocationName { get; set; }

        public void DisplayLatitude()
        {
            Console.WriteLine($"Lat: {coord.Latitude}");
        }

        public void DisplayLongitude()
        {
            Console.WriteLine($"Longitude: {coord.Longitude}");
        }

        public void DisplayLocation()
        {
            Console.WriteLine($"Location: {LocationName}");
        }
    }
}

See also