C#•4mo ago

✅ Pattern for PATCH API Parameter Existence Check

[ASP Core 8, .NET 8] I am developing some PATCH endpoints to update existing objects. I want my endpoint to only modify properties of the object that were set in the request - but null can only be a valid value to set. My problem seems to be that if I pass a URL parameter or payload with a parameter set, but it is blank, ASP is saying it is null. For example

[HttpPatch]
public IActionResult SomeMethod(
  [FromForm] string? someProperty
){}

[HttpPatch]
public IActionResult SomeMethod(
  [FromForm] string? someProperty
){}

With a payload

someProperty=

someProperty=

Then I would expect a blank string "". Instead, ASP gives me null. What pattern should I develop to make a proper PATCH endpoint that only utilizes parameters actually set in the payload?

1 Reply

nox7•4mo ago

I've decided to just go with a Payload object that has the properties for the original object being updated, but also "unmapped" "IsXSet" properties for each object property. The Controller will use [FromBody] JsonDocument jsonPayload and simply build my UpdateXPayload object and set the values and "Is" flags based on if they're in the JsonDocument.

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✅ Pattern for PATCH API Parameter Existence Check