C# · 12月 24, 2021

c# – 如何使用Reflection在IEnumerable上调用System.Linq.Enumerable.Count <>?

我有一堆IEnumerable集合,确切的数量和类型经常更改(由于自动代码生成).

它看起来像这样:

public class MyCollections { public System.Collections.Generic.IEnumerable<SomeType> SomeTypeCollection; public System.Collections.Generic.IEnumerable<OtherType> OtherTypeCollection; …

在运行时,我想确定每个Type和它的计数,而不必在每次代码生成后重写代码.所以我正在寻找使用反射的通用方法.我正在寻找的结果是这样的:

MyType: 23OtherType: 42

我的问题是我无法想象如何正确调用Count方法.这是我到目前为止:

// Handle to the Count method of System.Linq.Enumerable MethodInfo countMethodInfo = typeof(System.Linq.Enumerable).getmethod(“Count”,new Type[] { typeof(IEnumerable<>) }); PropertyInfo[] properties = typeof(MyCollections).GetProperties(); foreach (PropertyInfo property in properties) { Type propertyType = property.PropertyType; if (propertyType.IsGenericType) { Type genericType = propertyType.GetGenericTypeDeFinition(); if (genericType == typeof(IEnumerable<>)) { // access the collection property object collection = property.GetValue(someInstanceOfMyCollections,null); // access the type of the generic collection Type genericArgument = propertyType.GetGenericArguments()[0]; // make a generic method call for System.Linq.Enumerable.Count<> for the type of this collection MethodInfo localCountMethodInfo = countMethodInfo.MakeGenericMethod(genericArgument); // invoke Count method (this fails) object count = localCountMethodInfo.Invoke(collection,null); System.Diagnostics.Debug.WriteLine(“{0}: {1}”,genericArgument.Name,count); } } }解决方法 如果你坚持不懈努力; p

变化:

>如何获取泛型方法的countMethodInfo
> Invoke的参数

代码(注意obj是我的MyCollections实例):

MethodInfo countMethodInfo = typeof (System.Linq.Enumerable).getmethods().Single( method => method.Name == “Count” && method.IsStatic && method.GetParameters().Length == 1); PropertyInfo[] properties = typeof(MyCollections).GetProperties(); foreach (PropertyInfo property in properties) { Type propertyType = property.PropertyType; if (propertyType.IsGenericType) { Type genericType = propertyType.GetGenericTypeDeFinition(); if (genericType == typeof(IEnumerable<>)) { // access the collection property object collection = property.GetValue(obj,null); // access the type of the generic collection Type genericArgument = propertyType.GetGenericArguments()[0]; // make a generic method call for System.Linq.Enumerable.Count<> for the type of this collection MethodInfo localCountMethodInfo = countMethodInfo.MakeGenericMethod(genericArgument); // invoke Count method (this fails) object count = localCountMethodInfo.Invoke(null,new object[] {collection}); System.Diagnostics.Debug.WriteLine(“{0}: {1}”,count); } } }