/// <summary>
 ///   Constraints the URL parameter to valid <c>Guid</c> values.
 /// </summary>
 /// <param name="builder">The route builder.</param>
 /// <returns>The route builder.</returns>
 public static IParameterRouteBuilder Guid(this IParameterRouteBuilder builder)
 {
     return(builder.WithConstraint(GuidConstraint.Instance));
 }
 /// <summary>
 ///   Constraints the URL parameter to valid <c>Int32</c> values.
 /// </summary>
 /// <param name="builder">The route builder.</param>
 /// <returns>The route builder.</returns>
 public static IParameterRouteBuilder Int32(this IParameterRouteBuilder builder)
 {
     return(builder.WithConstraint(Int32Constraint.Instance));
 }