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// Copyright (c) Microsoft Corporation. All rights reserved. See License.txt in the project root for license information.
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading;
namespace System.Web.Mvc
{
internal static class TypeHelpers
{
private static readonly Dictionary<Type, TryGetValueDelegate> _tryGetValueDelegateCache = new Dictionary<Type, TryGetValueDelegate>();
private static readonly ReaderWriterLockSlim _tryGetValueDelegateCacheLock = new ReaderWriterLockSlim();
private static readonly MethodInfo _strongTryGetValueImplInfo = typeof(TypeHelpers).GetMethod("StrongTryGetValueImpl", BindingFlags.NonPublic | BindingFlags.Static);
public static readonly Assembly MsCorLibAssembly = typeof(string).Assembly;
public static readonly Assembly MvcAssembly = typeof(Controller).Assembly;
public static readonly Assembly SystemWebAssembly = typeof(HttpContext).Assembly;
// method is used primarily for lighting up new .NET Framework features even if MVC targets the previous version
// thisParameter is the 'this' parameter if target method is instance method, should be null for static method
public static TDelegate CreateDelegate<TDelegate>(Assembly assembly, string typeName, string methodName, object thisParameter) where TDelegate : class
{
// ensure target type exists
Type targetType = assembly.GetType(typeName, false /* throwOnError */);
if (targetType == null)
{
return null;
}
return CreateDelegate<TDelegate>(targetType, methodName, thisParameter);
}
public static TDelegate CreateDelegate<TDelegate>(Type targetType, string methodName, object thisParameter) where TDelegate : class
{
// ensure target method exists
ParameterInfo[] delegateParameters = typeof(TDelegate).GetMethod("Invoke").GetParameters();
Type[] argumentTypes = Array.ConvertAll(delegateParameters, pInfo => pInfo.ParameterType);
MethodInfo targetMethod = targetType.GetMethod(methodName, argumentTypes);
if (targetMethod == null)
{
return null;
}
TDelegate d = Delegate.CreateDelegate(typeof(TDelegate), thisParameter, targetMethod, false /* throwOnBindFailure */) as TDelegate;
return d;
}
public static TryGetValueDelegate CreateTryGetValueDelegate(Type targetType)
{
TryGetValueDelegate result;
_tryGetValueDelegateCacheLock.EnterReadLock();
try
{
if (_tryGetValueDelegateCache.TryGetValue(targetType, out result))
{
return result;
}
}
finally
{
_tryGetValueDelegateCacheLock.ExitReadLock();
}
Type dictionaryType = ExtractGenericInterface(targetType, typeof(IDictionary<,>));
// just wrap a call to the underlying IDictionary<TKey, TValue>.TryGetValue() where string can be cast to TKey
if (dictionaryType != null)
{
Type[] typeArguments = dictionaryType.GetGenericArguments();
Type keyType = typeArguments[0];
Type returnType = typeArguments[1];
if (keyType.IsAssignableFrom(typeof(string)))
{
MethodInfo strongImplInfo = _strongTryGetValueImplInfo.MakeGenericMethod(keyType, returnType);
result = (TryGetValueDelegate)Delegate.CreateDelegate(typeof(TryGetValueDelegate), strongImplInfo);
}
}
// wrap a call to the underlying IDictionary.Item()
if (result == null && typeof(IDictionary).IsAssignableFrom(targetType))
{
result = TryGetValueFromNonGenericDictionary;
}
_tryGetValueDelegateCacheLock.EnterWriteLock();
try
{
_tryGetValueDelegateCache[targetType] = result;
}
finally
{
_tryGetValueDelegateCacheLock.ExitWriteLock();
}
return result;
}
public static Type ExtractGenericInterface(Type queryType, Type interfaceType)
{
Func<Type, bool> matchesInterface = t => t.IsGenericType && t.GetGenericTypeDefinition() == interfaceType;
return (matchesInterface(queryType)) ? queryType : queryType.GetInterfaces().FirstOrDefault(matchesInterface);
}
public static object GetDefaultValue(Type type)
{
return (TypeAllowsNullValue(type)) ? null : Activator.CreateInstance(type);
}
public static bool IsCompatibleObject<T>(object value)
{
return (value is T || (value == null && TypeAllowsNullValue(typeof(T))));
}
public static bool IsNullableValueType(Type type)
{
return Nullable.GetUnderlyingType(type) != null;
}
private static bool StrongTryGetValueImpl<TKey, TValue>(object dictionary, string key, out object value)
{
IDictionary<TKey, TValue> strongDict = (IDictionary<TKey, TValue>)dictionary;
TValue strongValue;
bool retVal = strongDict.TryGetValue((TKey)(object)key, out strongValue);
value = strongValue;
return retVal;
}
private static bool TryGetValueFromNonGenericDictionary(object dictionary, string key, out object value)
{
IDictionary weakDict = (IDictionary)dictionary;
bool containsKey = weakDict.Contains(key);
value = (containsKey) ? weakDict[key] : null;
return containsKey;
}
public static bool TypeAllowsNullValue(Type type)
{
return (!type.IsValueType || IsNullableValueType(type));
}
}
}
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