如何更改LINQ查询中的返回类型
我正在寻找一种更改从返回类型的好方法 iEnumerable在anonymouStype中to ienumerable＆lt;（字符串类别，十进制平均值）＆gt;
/// <summary>
/// Gets the average price of each category's products.
/// </summary>
/// <returns>The average price of each category's products.</returns>
public static IEnumerable<(string Category, decimal averagePrice)> AveragePrice()
{
List<Product> products = GetListProducts();
var result = from p in products
group p by p.Category into g
select new { Category = g.Key, AveragePrice = g.Average(p => p.UnitPrice) };
return (IEnumerable<(string Category, decimal averagePrice)>)result;
}
逻辑很好，但我的问题是如何在没有匿名功能的情况下接收相同的结果 - 我认为我应该将查询更改为产品列表的LINQ操作。我目前正在尝试使用铸造来做到这一点，但这无效，因为我的单元测试抛出了invalidcastException。
我该如何正确执行？
I am searching for a good way to change the return type fromIEnumerable in anonymousType to IEnumerable<(string Category, decimal averagePrice)>
/// <summary>
/// Gets the average price of each category's products.
/// </summary>
/// <returns>The average price of each category's products.</returns>
public static IEnumerable<(string Category, decimal averagePrice)> AveragePrice()
{
List<Product> products = GetListProducts();
var result = from p in products
group p by p.Category into g
select new { Category = g.Key, AveragePrice = g.Average(p => p.UnitPrice) };
return (IEnumerable<(string Category, decimal averagePrice)>)result;
}
The logic is good but my problem is how to receive the same result without an anonymous function- I think I should change the query to a LINQ operation for products list. I am currently trying to do this with casting, but this doesn't work because my unit tests throw an InvalidCastException.
How can I do this properly?
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您投影到匿名类型，而不是元组，因此您不能从匿名类型的集合中投入到一组元组中。
最简单的修复程序是在选择中创建元组：
那么您不需要铸造（返回类型已经是元组的
iEnumerable）You are projecting to an anonymous type, not a tuple, so you can't cast from a collection of anonymous types to a collection of tuples.
The easiest fix is to create tuples in your select:
Then you don't need a cast (the return type will already be an
IEnumerableof your tuple)