System.ArgumentException: In a route parameter, '{' and '}' must be escaped with '{{' and '}}'. (Parameter 'routeTemplate')

Question

I'm porting an old API project to .NET Core 3.1 API project. All endpoints in old are working fine. While testing the new API on local IIS 10/Windows 10 I'm getting this error:

System.ArgumentException: In a route parameter, '{' and '}' must be escaped with '{{' and '}}'. (Parameter 'routeTemplate')

The specific route in question is not shown in the error. So I am including all routes here.

1. [Route("department/{id:int}")]
2. [Route("program/{deptId:int}")]
3. [Route(@"employee/{samId:regex(^[[A-Za-z0-9._-]]{3,30}$)}")]
4. [Route(@"homepage/{samId:regex(^[[a-zA-Z0-9_.-]]{3,30}$)}")]

On #2 and #3 I have double [ and double ] because I was getting error on those as well earlier when they were single.

Answer 1

According to the error message

System.ArgumentException: In a route parameter, '{' and '}' must be escaped with '{{' and '}}'. (Parameter 'routeTemplate')

you need to add one more {} in front, like this：

 [Route(@"test/{{samId:regex(^[[A-Za-z0-9._-]]{3,30}$)}}")]