ASP.NET Core 2.1 Swagger(swashbuckle) Url template optional parameter

Question

[HttpGet("commercial/{fromCcy}/{toCcy?}")]
public ActionResult Commercial(string fromCcy, string toCcy)

I have action "commercial" with optional parameter "toCcy" and swagger spec generates with required field. Is there any way to solve this problem?

Answer 1

When you use optional parameters, the best way is use [Fromquery]. For example:

[HttpGet("commercial")]
public ActionResult Commercial([FromQuery] OptionsViewModel viewModel)
{
...
}

public class OptionsViewModel
{
    public string FromCcy { get; set; }
    public string ToCcy { get; set; }
}

Then Swagger shows all parameters as optional:

Swagger UI Parameters:

Name    Description
FromCcy
string
(query)  

ToCcy
string
(query)