System.InvalidCastException: 'Specified cast is not valid.

[mkcse2012]

Hi,

I have tried a Xamarin.ios Bindings to create a nuget using a iOS SDK with Objective-c. I create a API definition file using sharpie tool. Then i introduce some implementation with methods as well. In the one of method I am getting the error "System.InvalidCastException: 'Specified cast is not valid.". So for that i would like to change whether ApiDefintion file is correct or not. And Here I attached the inheritance diagram is reference from right to Left. Kindly please help me to solve this issues.

NSObject <========= ProtectionPolicy <======= PasswordPolicy <======= BiometricPolicy

For example:

[Protocol]
[BaseType(typeof(NSObject))]
interface ProtectionPolicy
{
    [Abstract]
    [Export("policyId")]
    Identifier PolicyId { get; }

    [Abstract]
    [Export("policyType")]
    PolicyType PolicyType { get; } // This is Enum (three option)
}

[Protocol]
[BaseType(typeof(NSObject))]
interface PasswordPolicy : ProtectionPolicy
{
  .........
}

[Protocol]
[BaseType(typeof(NSObject))]
interface BiometricPolicy : PasswordPolicy
{
    [Abstract]
    [Export("enableAuthentication:error:")]
    bool EnableAuthentication(string password, out NSError error);

    [Abstract]
    [Export("getAuthenticationState")]
    AuthenticationState AuthenticationState { get; } // This is Enum (Three option)
}

[Protocol] interface Container { [Abstract] [Export("getName")] string Name { get; }

    [Abstract]
    [Export("getUserId")]
    string UserId { get; }

    [Abstract]
    [Export("getPolicy:")]
    IProtectionPolicy GetPolicy(out NSError error); // Reference IProtectionPolicy

    [Abstract]
    [Export("getDate:")]
    NSDate GetDate(out NSError error);
}