Micro Focus Visual COBOL 2.3 for Visual Studio 2015 > General Reference > Error Messages > Syntax Checking Error Messages > COBCH1501 - COBCH1600 > COBCH1561 - COBCH1580 > COBCH1564 First parameter to an extension method must be passed...

COBCH1564 First parameter to an extension method must be passed BY VALUE

The first parameter passed to an extension method must be a value parameter, not reference parameter.

To define an extension method:

Use the EXTENSION keyword in the method header.
The method must be in a static class that is not nested or generic. The method is implicitly static.
In the method body, the first parameter is the type to extend. It is always a value parameter.

Example:

The following extension method extends the string class, by adding a method to count the number of words in a string:

       class-id MyCount static.
       method-id CountWords extension. *> extension method is implicitly static
       procedure division using by value str as string 
                          returning wordCount as binary-long.
            set wordCount to str::Split(' ')::Length
       end method.
       end class.

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