[AttributeUsage(AttributeTargets.Parameter)]
public class SwaggerFileUploadAttribute : Attribute
{
public bool Required { get; private set; }
 
public SwaggerFileUploadAttribute(bool Required = true)
{
this.Required = Required;
}
}

/// <summary>
/// swagger file upload parameter filter
/// </summary>
public class SwaggerFileUploadFilter : IOperationFilter
{
public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
{
var parameters = apiDescription.ActionDescriptor.GetParameters();
foreach (HttpParameterDescriptor parameterDesc in parameters)
{
var fileUploadAttr = parameterDesc.GetCustomAttributes<SwaggerFileUploadAttribute>().FirstOrDefault();
if (fileUploadAttr != null)
{
operation.consumes.Add("multipart/form-data");
 
operation.parameters.Add(new Parameter
{
name = parameterDesc.ParameterName + "_file",
@in = "formData",
description = "file to upload",
required = fileUploadAttr.Required,
type = "file"
});
}
}
}
}