Choose diagnostic IDs

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:

• DiagnosticDescriptor.Id
• ObsoleteAttribute.DiagnosticId
• ExperimentalAttribute.DiagnosticId

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.