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Default Marshaling for Boolean Types

In general, marshaling base data types is straightforward. The Boolean data type is an exception. You can apply the MarshalAsAttribute attribute to marshal the Boolean type to any of the representations shown in the following table.

Enumeration type

Description of unmanaged format

UnmanagedType.Bool

4-byte integer value where any nonzero value represents true and 0 represents false. This is the default format of a Boolean field in a structure and of a Boolean parameter in platform invoke calls.

UnmanagedType.U1

1-byte integer value where the value 1 represents true and 0 represents false.

UnmanagedType.VariantBool

2-byte integer value where the value -1 represents true and 0 represents false. This is the default format of a Boolean parameter in COM calls.

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