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Choose diagnostic IDs

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A diagnostic ID is the string associated with a given diagnostic, such as a compiler error or a diagnostic that is produced by an analyzer.

The IDs are surfaced from various APIs, such as:

Diagnostic IDs are also used as identifiers in source, for example, from #pragma warning disable or .editorconfig files.

Considerations

  • Diagnostic IDs should be unique
  • Diagnostic IDs must be legal identifiers in C#
  • Diagnostic IDs should be less than 15 characters long
  • Diagnostic IDs should be of the form <PREFIX><number>
    • The prefix is specific to your project
    • The number represents the specific diagnostic

Note

It's a source breaking change to change diagnostic IDs, as existing suppressions would be ignored if the ID changed.

Don't limit your prefix to two-characters (such as CSXXXand CAXXXX). Instead, use a longer prefix to avoid conflicts. For example, the System.* diagnostics use SYSLIB as their prefix.