src/System.Web.Mvc/SingleServiceResolver.cs


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65

using System.Globalization;
using System.Web.Mvc.Properties;

namespace System.Web.Mvc
{
    internal class SingleServiceResolver<TService> : IResolver<TService>
        where TService : class
    {
        private TService _currentValueFromResolver;
        private Func<TService> _currentValueThunk;
        private TService _defaultValue;
        private Func<IDependencyResolver> _resolverThunk;
        private string _callerMethodName;

        public SingleServiceResolver(Func<TService> currentValueThunk, TService defaultValue, string callerMethodName)
        {
            if (currentValueThunk == null)
            {
                throw new ArgumentNullException("currentValueThunk");
            }
            if (defaultValue == null)
            {
                throw new ArgumentNullException("defaultValue");
            }

            _resolverThunk = () => DependencyResolver.Current;
            _currentValueThunk = currentValueThunk;
            _defaultValue = defaultValue;
            _callerMethodName = callerMethodName;
        }

        internal SingleServiceResolver(Func<TService> staticAccessor, TService defaultValue, IDependencyResolver resolver, string callerMethodName)
            : this(staticAccessor, defaultValue, callerMethodName)
        {
            if (resolver != null)
            {
                _resolverThunk = () => resolver;
            }
        }

        public TService Current
        {
            get
            {
                if (_resolverThunk != null)
                {
                    lock (_currentValueThunk)
                    {
                        if (_resolverThunk != null)
                        {
                            _currentValueFromResolver = _resolverThunk().GetService<TService>();
                            _resolverThunk = null;

                            if (_currentValueFromResolver != null && _currentValueThunk() != null)
                            {
                                throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture, MvcResources.SingleServiceResolver_CannotRegisterTwoInstances, typeof(TService).Name.ToString(), _callerMethodName));
                            }
                        }
                    }
                }
                return _currentValueFromResolver ?? _currentValueThunk() ?? _defaultValue;
            }
        }
    }
}