How can I pass more than one enum to a method that receives only one?

I'm wondering if the following is possible:

The method Regex.Match can receive an enum, so I can specify:

RegexOptions.IgnoreCase
RegexOptions.IgnorePatternWhiteSpace
RegexOptions.Multiline

What if I need to specify more than just one? (eg. I want my regex to be Multiline and I want i开发者_运维知识库t to ignore the pattern whitespace).

Could I use | operator like in C/C++?

You need to annotate it with [Flags] attribute and use | operator to combine them.

In the case you mentioned, you can do that because RegexOptions enum is annotated with it.

More References:

A helpful way to use the FlagsAttribute with enumerations

Example Snippet from above CodeProject article:

Definition:

[FlagsAttribute]
public enum NewsCategory : int 
{
    TopHeadlines =1,
    Sports=2,
    Business=4,
    Financial=8,
    World=16,
    Entertainment=32,
    Technical=64,
    Politics=128,
    Health=256,
    National=512
}

Use:

mon.ContentCategories = NewsCategory.Business | 
                        NewsCategory.Entertainment | 
                        NewsCategory.Politics;

Since it is an Enum with a Flags Attribute, you can use:

RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhiteSpace | RegexOptions.Multiline

If it is a Flags enum you need to to a bitwise OR:

var combine = RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhiteSpace | RegexOptions.Multiline;
myFunction(combine);

If this is not such an enum, you are out of luck.

See http://msdn.microsoft.com/en-us/library/yd1hzczs.aspx for details.

Don't use &, use | (you want to do a bit-wise Boolean OR).

Just to enhance the answers a bit, the Flags attribute is not a requirement. Every enum value can be combined with the bitwise | operator. The Flags attribute only makes the enum a bit more readable when converted into a string (eg. instead of seeing a number with the bitwise result as a number, you see the selected flags combined).

To test if a condition is set you normally would use a bitwise &. This will also work without the Flags attribute.

In the MSDN documentation for this attribute there is an example of two enums, one with and the other without it: FlaggsAttribute.