System.IsNullGuid(Guid) Method
Version: Available or changed with runtime version 1.0.
Indicates whether a value has been assigned to a GUID. A null GUID that consists only of zeros is valid but must never be used for references.
Syntax
Ok := System.IsNullGuid(Guid: Guid)
Note
This method can be invoked without specifying the data type name.
Parameters
Guid
Type: Guid
The GUID that you want to check whether it is null.
Return Value
Ok
Type: Boolean
Remarks
A GUID is a 16-byte binary data type that can be logically grouped into the following subgroups: 4byte-2byte-2byte-2byte-6byte.
The GUID data type is useful when you want to uniquely identify data so that it can be exchanged with external applications. For example, if you want to transfer an item catalog to an external application, you add a GUID field to the record in the table and use it as the primary reference when you communicate with the external application.
Example
The following example initializes two variables named validGuid and nullGuid. The validGuid variable is assigned a valid GUID value, and the nullGuid variable is assigned a null GUID that consists of only zeros. The IsNullGuid method determines whether the GUID that's contained in the validGuid variable is null. In this case, the GUID validGuid isn't null so a message that states that the GUID isn't null is displayed and the value is displayed. The method then checks the nullGuid parameter. This time, a message that states that the GUID is null, is displayed because the GUID is a null GUID that consists of only zeros.
var
validGuid: Guid;
nullGuid: Guid;
unInitializedGuid: Guid;
begin
validGuid := '{FC841BE6-0ADA-46C4-A6A9-142AEC211613}';
nullGuid := '{00000000-0000-0000-0000-000000000000}';
if IsNullGuid(validGuid) then
Message('The GUID is null');
else
Message('The GUID isn't null.\\' + StrSubstNo('The value is %1.', validGuid));
if IsNullGuid(nullGuid) then
Message('The GUID is null');
if IsNullGuid(unInitializedGuid) then
Message('The GUID is null');
end;