asp.net web api2 - Data annotations in Swagger

Question

I am using ASP.NET and Swagger that exposes a complex type that accepts a POST. It has a number of string fields that have different restricted lengths. How can I reflect that in the Swagger UI?

Answer 1

You can annotate the properties with the StringLengthAttribute from System.ComponentModel.DataAnnotations.

For instance:

[StringLength(10)]
public String Name {get;set;}

will become:

"name": {
    "minLength": 0,
    "maxLength": 10,
    "type": "string"
}

And this:

[StringLength(10, MinimumLength = 5)]
public String Name {get;set;}

becomes:

"name": {
    "minLength": 5,
    "maxLength": 10,
    "type": "string"
}

Besides StringLength Swashbuckle also supports the Range and RegularExpression attributes.

Update

MaxLength does not work. StringLength does. However, discovering this information in Swagger UI is a bit clumsy. You have to navigate to the Model of your object and then hover over the property: