Default model example in Swashbuckle (Swagger)

I know this thread is quite old, but I wanted to share my solution which creates a custom constructor just for the Swagger example schema.

In my model:

/// <summary>
/// Supply a custom constructor for Swagger where you can apply defaults to control the example schema.  
/// The constructor must have one parameter of type System.Reflection.ParameterInfo[].
/// Note: Setting a property to null will prevent it from showing in the Swagger example.
/// </summary>System.Reflection.ParameterInfo[].
/// </summary>
public class SwaggerConstructor : Attribute { }

In SwaggerConfig.cs:

c.SchemaFilter<ApplySchemaVendorExtensions>();

The schema extension:

    public class ApplySchemaVendorExtensions : ISchemaFilter
{
    public void Apply(Schema schema, SchemaRegistry schemaRegistry, Type type)
    {
        ConstructorInfo constructor = type.GetConstructors().FirstOrDefault(c => c.GetCustomAttribute<SwaggerConstructor>() != null);
        if (constructor != null)
        {
            schema.example = constructor.Invoke(new object[] { constructor.GetParameters() });
        }
    }
}

Usage:

    [SwaggerConstructor]
    public MyClass(System.Reflection.ParameterInfo[] decoy) : base()
    {
        MyProperty = false;
    }

An example Model Schema can be defined by implementing ISchemaFilter and registering it using the following:

httpConfig 
    .EnableSwagger(c =>
         {
             c.SchemaFilter<AddSchemaExamples>()
         });

An example implementation is provided here:

public class AddSchemaExamples : ISchemaFilter
{
    public void Apply(Schema schema, SchemaRegistry schemaRegistry, Type type)
    {
        if (type == typeof(Product))
        {
            schema.example = new Product
                {
                    Id = 123,
                    Type = ProductType.Book,
                    Description = "Treasure Island",
                    UnitPrice = 10.0M
                };
        }
    }
}

Source: https://github.com/domaindrivendev/Swashbuckle/issues/162

Well the code of vgaspar.trivix did not work completly for me, the default values did not get set for the schema. Also i got an NullPointerException. I managed to get it working as intended by editing the Apply method and manipulated the schemaRegistry like this:

public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
{
    if (operation.parameters == null)
        return;
    IDictionary<string, object> parameterValuePairs =
    GetParameterValuePairs(apiDescription.ActionDescriptor);

    foreach (var param in operation.parameters)
    {
        if (param.schema != null && param.schema.@ref != null)
        {
            string schemaName = [email protected]('/').LastOrDefault();
            if (schemaRegistry.Definitions.ContainsKey(schemaName))
                foreach (var props in schemaRegistry.Definitions[schemaName].properties)
                {
                    if (parameterValuePairs.ContainsKey(props.Key))
                        props.Value.@default = parameterValuePairs[props.Key];
                }
        }
        var parameterValuePair = parameterValuePairs.FirstOrDefault(p => p.Key.IndexOf(param.name, StringComparison.InvariantCultureIgnoreCase) >= 0);
        param.@default = parameterValuePair.Value;
    }
}

I managed to get this working by following what's on this link:

https://github.com/domaindrivendev/Swashbuckle/issues/69#issuecomment-53953785

In short this is what needs to be done:

1. Create the classes SwaggerDefaultValue and AddDefaultValues as described in the link. Some changes that I did:

   public class SwaggerDefaultValue : Attribute
   {
       public string Name { get; set; }
       public string Value { get; set; }
   
       public SwaggerDefaultValue(string value)
       {
           this.Value = value;
       }
   
       public SwaggerDefaultValue(string name, string value) : this(value)
       {
           this.Name = name;
       }
   }
   
   public class AddDefaultValues : IOperationFilter
   {
       public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
       {
           IDictionary<string, object> parameterValuePairs =
           GetParameterValuePairs(apiDescription.ActionDescriptor);
   
           foreach (var param in operation.parameters)
           {
               var parameterValuePair = parameterValuePairs.FirstOrDefault(p => p.Key.IndexOf(param.name, StringComparison.InvariantCultureIgnoreCase) >= 0);
               param.@default = parameterValuePair.Value;
           }
       }
   
       private IDictionary<string, object> GetParameterValuePairs(HttpActionDescriptor actionDescriptor)
       {
           IDictionary<string, object> parameterValuePairs = new Dictionary<string, object>();
   
           foreach (SwaggerDefaultValue defaultValue in actionDescriptor.GetCustomAttributes<SwaggerDefaultValue>())
           {
               parameterValuePairs.Add(defaultValue.Name, defaultValue.Value);
           }
   
           foreach (var parameter in actionDescriptor.GetParameters())
           {
               if (!parameter.ParameterType.IsPrimitive)
               {
                   foreach (PropertyInfo property in parameter.ParameterType.GetProperties())
                   {
                       var defaultValue = GetDefaultValue(property);
   
                       if (defaultValue != null)
                       {
                            parameterValuePairs.Add(property.Name, defaultValue);
                       }
                   }
               }
           }
   
           return parameterValuePairs;
       }
   
       private static object GetDefaultValue(PropertyInfo property)
       {
           var customAttribute = property.GetCustomAttributes<SwaggerDefaultValue>().FirstOrDefault();
   
           if (customAttribute != null)
           {
               return customAttribute.Value;
           }
   
           return null;
       }
   }
   

   2. Edit your SwaggerConfig and add the AddDefaultValues class to the OperationFilters:

      GlobalConfiguration.Configuration
          .EnableSwagger(c => {
                ...
                c.OperationFilter<AddDefaultValues>()
                ...
           });
      

   3. Now for the parameters I want default values I just add the following:

      public IHttpActionResult Put([FromBody]Pet pet)
      {
         ...
         return Ok();
      }
      
      public class Pet {
          [SwaggerDefaultValue("doggie")]
          public string Name { get; set; }
      
          [SwaggerDefaultValue("available")]
          public string Status;
      
          ...
      }