What is | in C# here?

Question

In the following code block there are a few bitwise OR's. I've never used them before so I was trying to understand what the code block meant.

    Document doc = new Document("CleanupOptions.docx");
    doc.MailMerge.CleanupOptions = MailMergeCleanupOptions.RemoveUnusedRegions |
    MailMergeCleanupOptions.RemoveUnusedFields |
    MailMergeCleanupOptions.RemoveContainingFields;
    doc.MailMerge.ExecuteWithRegions(dataSet);

So in that block above, if I used doc.MailMerge.CleanupOptions, how would I pick any of the statements that the CleanupOptions are equal to? Or are they all combined?

This Q/A has a good explanation of enumerations with [Flags]: http://stackoverflow.com/questions/8447/what-does-the-flags-enum-attribute-mean-in-c — Wiseguy, Apr 01 '15 at 13:12
it's about [flags](https://msdn.microsoft.com/en-US/library/cc138362.aspx) — Thomas Ayoub, Apr 01 '15 at 13:12
Assuming that `CleanupOptions` is a bitfield enumeration, this simply concats the constants... — Binkan Salaryman, Apr 01 '15 at 13:13

score 0 · Answer 1 · answered Apr 01 '15 at 13:12

0

They are all combined. An enum can be marked with the [FlagsAttribute] which allows combination of values:

https://msdn.microsoft.com/en-us/library/system.flagsattribute(v=vs.110).aspx

answered Apr 01 '15 at 13:12

nodots

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score 0 · Answer 2 · answered Apr 01 '15 at 13:14

0

The MailMergeCleanupOptions is an enum with the FlagsAttribute specified. This allows you to do bit-wise ors to join the values into a collection. Normally the values are powers of two or a combination of flags.

answered Apr 01 '15 at 13:14

John Taylor

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It's not really the `[Flags]` attribute doing that though, that attribute does very little. It's the enum itself combined with how it is interpreted by the consuming code. – harold Apr 01 '15 at 13:52
The compiler will complain if you do a bitwise or on an enum that does not have the [Flags] attribute. – John Taylor Apr 01 '15 at 14:26
No it doesn't, you even made me doubt myself enough that I went to try it – harold Apr 01 '15 at 14:41
Must be ReSharper that complains. Sometimes I lose track which one is generating which warnings. – John Taylor Apr 01 '15 at 14:45

What is | in C# here?

2 Answers2