Problem statement

In enterprise environments, database scaffolding tools often auto-generate data models. If a developer edits these generated files, the scaffolding tool overwrites their custom logic during the next run. You have an auto-generated Invoice model. You need to inject a custom business rule to flag invoices with a negative total without modifying the auto-generated file.

Task requirements

• Provide the signature for an optional partial method named Validate in the generated code.

• Invoke Validate() from inside the existing Process() method.

• Implement the Validate method in the custom developer file to check if Total < 0.

• Print a warning if the total is negative, otherwise print a validation success message.

Constraints

• You must use the partial keyword on the Invoice class in both locations.

• You must use the partial keyword on the Validate method.

• You must use a file-scoped namespace named Business.Models in both class files.

• You must organize the solution across three distinct files: the execution script, the generated model, and the custom developer logic.

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Get hints

• For partial classes to merge, they must share the exact same namespace. Using a file-scoped namespace like namespace Business.Models; in both files is the cleanest way to do this.

• The signature in the generated file should look exactly like this: partial void Validate();

• Partial methods are optional; if you don't implement the body in the custom file, the compiler will simply remove the call from the generated code.