swagger error: Conflicting schemaIds: Duplicate schemaIds detected for types A and B

Using Web API and using swashbuckle to generate swagger documentation, I defined two different classes with the same name in two different namespaces. when I open swagger page in my browser it says

> Conflicting schemaIds: Duplicate schemaIds detected for types A and B. See the config setting - "UseFullTypeNameInSchemaIds" for a potential workaround

full message:

> 500 : {"Message":"An error has occurred.","ExceptionMessage":"Conflicting schemaIds: Duplicate schemaIds detected for types A and B. See the config setting - "UseFullTypeNameInSchemaIds" for a potential workaround","ExceptionType":"System.InvalidOperationException","StackTrace":" at Swashbuckle.Swagger.SchemaRegistry.CreateRefSchema(Type type)\r\n at Swashbuckle.Swagger.SchemaRegistry.CreateInlineSchema(Type type)\r\n at Swashbuckle.Swagger.SchemaRegistry.b__1f(JsonProperty prop)\r\n at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer)\r\n at Swashbuckle.Swagger.SchemaRegistry.CreateObjectSchema(JsonObjectContract jsonContract)\r\n at Swashbuckle.Swagger.SchemaRegistry.CreateDefinitionSchema(Type type)\r\n at Swashbuckle.Swagger.SchemaRegistry.GetOrRegister(Type type)\r\n at Swashbuckle.Swagger.SwaggerGenerator.CreateOperation(ApiDescription apiDesc, SchemaRegistry schemaRegistry)\r\n at Swashbuckle.Swagger.SwaggerGenerator.CreatePathItem(IEnumerable1 apiDescriptions, SchemaRegistry schemaRegistry)\r\n at Swashbuckle.Swagger.SwaggerGenerator.<>c__DisplayClass7.<GetSwagger>b__4(IGrouping2 group)\r\n at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer)\r\n at Swashbuckle.Swagger.SwaggerGenerator.GetSwagger(String rootUrl, String apiVersion)\r\n at Swashbuckle.Application.SwaggerDocsHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Net.Http.HttpMessageInvoker.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Web.Http.Dispatcher.HttpRoutingDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Net.Http.DelegatingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Web.Http.HttpServer.d__0.MoveNext()"} http://localhost:24215/swagger/docs/v1

I don't want to change my classes' names. How can I fix it?

Every class in the swagger JSON must have a unique schemaId.

Swashbuckler tries to just use the class name as a simple schemaId, however if you have two classes in different namespaces with the same name (as you do) this will not work.

As the error suggests, you can use the config setting "UseFullTypeNameInSchemaIds*" for a potential workaround (Update: not available in recent versions)

In newer versions you can achieve the same behavior via options.CustomSchemaIds(x => x.FullName).

Here is an example:

   services.ConfigureSwaggerGen(options =>
   {
       //your custom configuration goes here

...

  // UseFullTypeNameInSchemaIds replacement for .NET Core
       options.CustomSchemaIds(x => x.FullName);
   });

for more information http://wegotcode.com/microsoft/swagger-fix-for-dotnetcore/

I finally found a way in swagger configs. Go to App_Start\SwaggerConfig.cs file and under EnableSwagger lambda expression add this line:

c.SchemaId(x => x.FullName);

Full code is like this:

GlobalConfiguration.Configuration 
    .EnableSwagger(c =>
    {
        // your configs...

        c.SchemaId(x => x.FullName);
        
        // other configs...
    })
    .EnableSwaggerUi(c =>
        // ....
    });

I am using Asp.net Core 2.1. This error resulted when I tried to show Swagger UI.

I solved the problem this way:

In Starup.cs, in ConfigureServices() add c.CustomSchemaIds(i => i.FullName);

see example below:

services.AddSwaggerGen(c =>
        {
            c.SwaggerDoc("v1", new Info
            {
                Title = "ASP.NET Core 2.1+ ConsumerApp API",
                Version = "v1"
            });
            // Set the comments path for the Swagger JSON and UI.
            var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
            var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
            c.IncludeXmlComments(xmlPath);
            c.CustomSchemaIds(i => i.FullName);
        });

If you comment out or add:

c.UseFullTypeNameInSchemaIds();

In that section, it seems to do same thing.

For Swashbuckle.AspNetCore 5.2.1 (on .NET Core 3.1), the Swashbuckle configuration API seems to lack the options described in the older solutions. Instead, the following change in the Startup.cs worked for me:

  services.AddSwaggerGen(c =>
  {
     // Existing configuration

     // Tweak to the Schema generator
     c.SchemaGeneratorOptions = new SchemaGeneratorOptions {SchemaIdSelector = type => type.FullName};
  }

If your model contains generic types, consider using Type.ToString() instead of Type.FullName to get rid of assembly information generated for generic parameter type and make your schema ids more consistent.

services.AddSwaggerGen(options =>
{
    options.CustomSchemaIds(type => type.ToString());
});

Example showing the difference on List<string>:

Console.WriteLine(typeof(List<string>).FullName);
Console.WriteLine(typeof(List<string>).ToString());

// Output:
//    System.Collections.Generic.List`1[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]
//    System.Collections.Generic.List`1[System.String]