Question

我有BindingSource DataSource（定义为对象）在运行时可以是任何类型的IEnumerable类（例如IList<Foo>）。我需要将其转换为IQueryable<T>，以便将其传递给通用扩展名：

IOrderedQueryable<TEntity> OrderUsingSortExpression<TEntity>(this IQueryable<TEntity> source, string sortExpression) where TEntity : class

到目前为止，我有这个：

string order = "Message ASC";
Type thetype = bsTotalBindingSource.DataSource.GetType().GetGenericArguments()[0];
IEnumerable<object> totalDataSource = ((IEnumerable<object>)(bsTotalBindingSource.DataSource));
//Blowing up on this next line with 'System.Linq.Queryable is not a GenericTypeDefinition. MakeGenericType may only be called on a type for which Type.IsGenericTypeDefinition is true.'
MethodInfo asQueryableMethod = typeof(Queryable).MakeGenericType(thetype).GetMethod("AsQueryable", BindingFlags.Static | BindingFlags.Public, null, new[] { typeof(IQueryable<>) }, null); 
MethodInfo genericAsQueryableMethod = asQueryableMethod.MakeGenericMethod(thetype);
MethodInfo orderUsingSortExpressionMethod = GetType().GetMethod("OrderUsingSortExpression");
MethodInfo genericUsingSortExpressionMethod = orderUsingSortExpressionMethod.MakeGenericMethod(thetype);
bsTotalBindingSource.DataSource = genericUsingSortExpressionMethod.Invoke(this, new object[] { genericAsQueryableMethod.Invoke(totalDataSource, null), order });

正如您所看到的，此处的最终目标是能够从DataSource中获取某些内容，将IEnumerable<T>的RuntimeType设置为T可以为什么，然后调用AsQueryable<T>它可以传递给接受IQueryable<T>的函数。

EDIT 经过四处寻找具体找到我正在寻找的方法后，我对这个问题有了更深入的了解。它现在看起来像这样：

string order = "Message ASC";
Type thetype = bsTotalBindingSource.DataSource.GetType().GetGenericArguments()[0];
//Returns the AsQueryable<> method I am looking for
MethodInfo asQueryableMethod = typeof(Queryable).MakeGenericType(thetype).GetMethods()[1]; 
MethodInfo genericAsQueryableMethod = asQueryableMethod.MakeGenericMethod(thetype);
MethodInfo orderUsingSortExpressionMethod = typeof(SortExtension)GetType().GetMethods()[0];
MethodInfo genericUsingSortExpressionMethod = orderUsingSortExpressionMethod.MakeGenericMethod(thetype);
bsTotalBindingSource.DataSource = genericUsingSortExpressionMethod.Invoke(this, new object[] { genericAsQueryableMethod
//blows up here with 'Object of type 'System.RuntimeType' cannot be converted to type 'System.Collections.Generic.IEnumerable`1[LogRecordDTO]'.'
.Invoke(bsTotalBindingSource.DataSource, new object[] {thetype}), order });

Answer 1

您说要将IEnumerable<T>转换为IQueryable<T>，其中T的类型未知。

private void Test<T>(IEnumerable<T> x)
{
    var queryableX = x.AsQueryable();
}

注意：您需要using System.Linq。

Answer 2

我认为以下内容可能有效：

// Get generic type argument for everything
Type theType = bsTotalBindingSource.DataSource
    .GetType().GetGenericArguments()[0];

// Convert your IEnumerable<?>-in-an-object to IQueryable<?>-in-an-object
var asQueryable =
    // Get IEnumerable<?> type
    typeof(IEnumerable<>)
    .MakeGenericType(new[] { theType })
    // Get IEnumerable<?>.AsQueryable<?> method
    .GetMethod(
        "AsQueryable",
        new Type[] { theType },
        System.Reflection.BindingFlags.Static |
        System.Reflection.BindingFlags.Public)
    // Call on the input object
    .Invoke(bsTotalBindingSource.DataSource, new object[0]);

// Sort this queryable
var asSortedQueryable =
    // Get the YourType<?> generic class your sorting generic method is in?
    // If your class isn't generic I guess you can skip the MakeGenericType.
    typeof(yourtype)
    .MakeGenericType(new[] { theType })
    // Get the OrderUsingSortExpression<?> method
    .GetMethod(
        "OrderUsingSortExpression",
        new Type[] { theType },
        System.Reflection.BindingFlags.Static |
        System.Reflection.BindingFlags.Public)
    // Call on the IQueryable<?> object
    .Invoke(dataSource, new object[] { order });

// Set this object to the data source
bsTotalBindingSource.DataSource = asSortedQueryable;

作为免责声明，我对此并不是很清楚。例如从AsQueryable<T>获取IEnumerable<T>时，是否需要传递泛型参数？但我做相信你想要做的事情是可能的，并且需要反思，我做认为这是大致正确的。

Answer 3

我认为最简单的方法是重载（或添加扩展方法）到你想要调用的方法，将IEnumerable作为参数。然后只需从中调用另一个方法。这是我的意思的一个例子。

public class MyTestClass
{
    public void Run()
    {
        List<string> myList = new List<string>() { "one", "two" };

        object myListObject = (object)myList;

        Test(myListObject);
    }

    private void Test(object myListObject)
    {
        Type myGenericType = myListObject.GetType().GetGenericArguments().First();

        MethodInfo methodToCall = typeof(MyTestClass).GetMethods().Single(
            method => method.Name.Equals("GenericMethod") && method.GetParameters().First().Name.Equals("myEnumerableArgument"));

        MethodInfo genericMethod = methodToCall.MakeGenericMethod(myGenericType);

        genericMethod.Invoke(this, new object[] { myListObject });
    }

    public void GenericMethod<T>(IQueryable<T> myQueryableArgument)
    {
    }

    public void GenericMethod<T>(IEnumerable<T> myEnumerableArgument)
    {
        GenericMethod<T>(myEnumerableArgument.AsQueryable());
    }
}

将IEnumerable <t>转换为IQueryable <t>，其中T未知</t> </t>

3 个答案: