When a web api expects an int value, if the client sends null or empty string in JSON, it is automatically converted to 0. How can I prevent this? Is there such a configuration? I want it to throw an error since it is not what it expects.
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3 Answers
You can annotate your DTO / property with the JsonPropery attribute and mark it as required:
public class MyDto
{
[JsonProperty(Required = Required.Always)]
public int RequiredProperty { get;set; }
}
With this attribute, JsonConvert.DeserializeObject() will throw an exception if no value for the property is specified in the JSON string.
See here for an example: https://dotnetfiddle.net/TstCau
2 Comments
John L.
Actually the problem is misuse of the api by the client so that they might send null or "" for a required int (not int?). This causes it to be deserialized to 0, which is wrong. As far as I understand, your proposed solution does not prevent this. In short, what I want is to prevent this automaic conversion behavior.
M4N
@JohnL.I still get an exception, when I modify the sample and pass
'RequiredProperty' : ''. If I understand correctly, that's what you want. (see dotnetfiddle.net/Fhy5Bf)You can allow null inside an integer by declaring it as "int?"
After this you can just check if the variable is equal to null and give an error message.
2 Comments
John L.
I would not want to malform every data model and add such a check. Because what I want to do is to prevent erroneous use of the api so that when accidentally null or "" is sent, it will not be perceived as 0. So, in short, I want to change this automatic conversion behavior.
Rick
Oh ok I misunderstood the question then. I'm sorry but I don't know if that is possible.
This solution is also rather a hack and should not be used on a regular basis. But here we go.
I had a problem - I wanted to accept enums on my API as strings, but wanted to have them in my code as enums, not strings.
I just put an extra property (may put some data attribute there, like [NotMapped]) and overrode getters and setters like the following
/// <summary>
/// Required. A type of the metric for which data is requested.
/// </summary>
public Metrics MetricType { get; set; }
[Required]
/// <summary>
/// Alias for MetricType.
/// </summary>
public string Type
{
get
{
return MetricType.ToString();
}
set
{
try
{
MetricType = value.ToEnum<Metrics>();
}
catch (System.Exception)
{
throw new ArgumentException("Invalid Type parameter.");
}
}
}
I think you may override conversion logic like that. Check your string for null or empty and assign proper value to your int.
