Hide parameter from Swagger (Swashbuckle)

Question

I have a C# .NET 5.0 ASP.NET Core Web API application with "Enable OpenAPI support" selected. I want to hide the optional parameter in the below example from what shows up on the swagger page. I have found numerous posts about hiding a property or the controller but none of these solutions seem to work for just the parameter in the given code:

[HttpGet]
[Route("search")]
[Authorize]
public async Task<IActionResult> Search(string query, string optional = "")
{
   return OK();
}

Answer 1

You can create a custom attibute and an operation filter inhering from Swashbuckle.AspNetCore.SwaggerGen.IOperationFilter to exclude the desired parameters from swagger.json generation

public class OpenApiParameterIgnoreAttribute : System.Attribute
{
}

public class OpenApiParameterIgnoreFilter : Swashbuckle.AspNetCore.SwaggerGen.IOperationFilter
{
    public void Apply(Microsoft.OpenApi.Models.OpenApiOperation operation, Swashbuckle.AspNetCore.SwaggerGen.OperationFilterContext context)
    {
        if (operation == null || context == null || context.ApiDescription?.ParameterDescriptions == null)
            return;

        var parametersToHide = context.ApiDescription.ParameterDescriptions
            .Where(parameterDescription => ParameterHasIgnoreAttribute(parameterDescription))
            .ToList();

        if (parametersToHide.Count == 0)
            return;

        foreach (var parameterToHide in parametersToHide)
        {
            var parameter = operation.Parameters.FirstOrDefault(parameter => string.Equals(parameter.Name, parameterToHide.Name, System.StringComparison.Ordinal));
            if (parameter != null)
                operation.Parameters.Remove(parameter);
        }
    }

    private static bool ParameterHasIgnoreAttribute(Microsoft.AspNetCore.Mvc.ApiExplorer.ApiParameterDescription parameterDescription)
    {
        if (parameterDescription.ModelMetadata is Microsoft.AspNetCore.Mvc.ModelBinding.Metadata.DefaultModelMetadata metadata)
        {
            return metadata.Attributes.ParameterAttributes.Any(attribute => attribute.GetType() == typeof(OpenApiParameterIgnoreAttribute));
        }

        return false;
    }
}

Put it in your controller's parameter

[HttpGet]
[Route("search")]
[Authorize]
public async Task<IActionResult> Search(string query, [OpenApiParameterIgnore] string optional = "")
{
    return Ok();
}

Then configure it in Status.cs

    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API Title", Version = "v1" });
        c.OperationFilter<OpenApiParameterIgnoreFilter>();
    });