CA2230: Use params for variable arguments
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
| Item | Value |
|---|---|
| RuleId | CA2230 |
| Category | Microsoft.Usage |
| Breaking change | Breaking |
Cause
A public or protected type contains a public or protected method that uses the VarArgs calling convention.
Note
This rule has been deprecated. For more information, see Deprecated rules.
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);
for(int i = 0; i < argumentIterator.GetRemainingCount(); i++)
{
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]);
}
}
}
}