CA2230: Use params for variable arguments

Cause

A public or protected type contains a public or protected method that uses the VarArgs calling convention.

Rule description

The VarArgs calling convention is used with certain method definitions that take a variable number of parameters. A method using the VarArgs calling convention is not Common Language Specification (CLS) compliant and might not be accessible across programming languages.

In C#, the VarArgs calling convention is used when a method's parameter list ends with the __arglist keyword. Visual Basic does not support the VarArgs calling convention, and C++ allows its use only in unmanaged code that uses the ellipse ... notation.

How to fix violations

To fix a violation of this rule in C#, use the params keyword instead of __arglist.

When to suppress warnings

Do not suppress a warning from this rule.

Example

The following example shows two methods, one that violates the rule and one that satisfies the rule.

using System;

[assembly: CLSCompliant(true)]
namespace UsageLibrary
{
    public class UseParams 
    {
        // This method violates the rule.
        [CLSCompliant(false)]
        public void VariableArguments(__arglist) 
        { 
            ArgIterator argumentIterator = new ArgIterator(__arglist);
            while (argumentIterator.GetRemainingCount() > 0)
            { 
                Console.WriteLine(__refvalue(argumentIterator.GetNextArg(), string));
            } 
        }

        // This method satisfies the rule.
        public void VariableArguments(params string[] wordList)
        { 
            for(int i = 0; i < wordList.Length; i++) 
            { 
                Console.WriteLine(wordList[i]);
            } 
        }
    }
}

See also

• System.Reflection.CallingConventions
• Language Independence and Language-Independent Components