CA2201: Do not raise reserved exception types
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CA2201: Do not raise reserved exception types








Breaking Change


A method raises an exception type that is too general or that is reserved by the runtime.

The following exception types are too general to provide sufficient information to the user:

The following exception types are reserved and should be thrown only by the common language runtime:

Do Not Throw General Exceptions

If you throw a general exception type, such as Exception or SystemException in a library or framework, it forces consumers to catch all exceptions, including unknown exceptions that they do not know how to handle.

Instead, either throw a more derived type that already exists in the framework, or create your own type that derives from Exception.

Throw Specific Exceptions

The following table shows parameters and which exceptions to throw when you validate the parameter, including the value parameter in the set accessor of a property:

Parameter Description


null reference 


Outside the allowed range of values (such as an index for a collection or list)


Invalid enum value


Contains a format that does not meet the parameter specifications of a method (such as the format string for ToString(String))


Otherwise invalid


When an operation is invalid for the current state of an object    throw System.InvalidOperationException

When an operation is performed on an object that has been disposed    throw System.ObjectDisposedException

When an operation is not supported (such as in an overridden Stream.Write in a Stream opened for reading)    throw System.NotSupportedException

When a conversion would result in an overflow (such as in a explicit cast operator overload)    throw System.OverflowException

For all other situations, consider creating your own type that derives from Exception and throw that.

To fix a violation of this rule, change the type of the thrown exception to a specific type that is not one of the reserved types.

Do not suppress a warning from this rule.

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