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namespace System.Web.Mvc {
using System.Globalization;
using System.Web.Mvc.Resources;
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;
}
}
}
}
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