The signature of an operation changes if the page contains one or more unbound fields in the root content area. If there are unbound fields, then the names from the SourceExpr property for the unbound fields are added as the first parameters to the operation. They are added according to the tab order of the page. For an example, see the Item Journal.
This argument is a filter on the primary key and returns the first record that matches the filter. When special characters, such as an apostrophe, equal sign, or ampersand, are part of the key, you must surround the argument with quotation marks.
For example, when writing C# code, in addition to standard quotation marks for strings, you should also provide additional single quotes around a value, such as "'A&B'".
This operation does not return a fault when a matching record is not present. Instead, it returns no value. In C#, you should test if the result is a null reference. Otherwise, you may get a NullReferenceException exception.
Faults are possible if they are generated by the C/AL code.