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

app.UseSwagger();
app.UseSwaggerUI(c =>
{
 c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});

// POST api/values
[HttpPost]
public void Post(IFormFile file)
{
 //TODO:Save file...
}
// PUT api/values/5
[HttpPut("{id}")]
public void Put(int id, IFormFile file)
{
 //TODO:Save file...
}

public class SwaggerFileUploadFilter : IOperationFilter
{
 public void Apply(Operation operation, OperationFilterContext context)
 {
  if (!context.ApiDescription.HttpMethod.Equals("POST", StringComparison.OrdinalIgnoreCase) &&
   !context.ApiDescription.HttpMethod.Equals("PUT", StringComparison.OrdinalIgnoreCase))
  {
   return;
  }
  var fileParameters = context.ApiDescription.ActionDescriptor.Parameters.Where(n => n.ParameterType == typeof(IFormFile)).ToList();
  if (fileParameters.Count < 0)
  {
   return;
  }
  operation.Consumes.Add("multipart/form-data");
  foreach (var fileParameter in fileParameters)
  {
   var parameter = operation.Parameters.Single(n => n.Name == fileParameter.Name);
   operation.Parameters.Remove(parameter);
   operation.Parameters.Add(new NonBodyParameter
   {
    Name = parameter.Name,
    In = "formData",
    Description = parameter.Description,
    Required = parameter.Required,
    Type = "file"
   });
  }
 }
}