如何将List转换为IEnumerable？求修复对象List提取整数函数

Hey there! Let's work through this problem together. It sounds like you're trying to write a function that pulls integers out of a List<object> but you're stuck on converting the list to IEnumerable and getting the function to run correctly—let's fix that right away.

The Simplest Approach: Use OfType<int>() #

The easiest way to get only integer values from your List<object> is using LINQ's OfType<T> method. This method does two things: it filters the collection to only include elements that are of type int, and it automatically casts those elements to int for you. Plus, since List<object> already implements IEnumerable<object>, you don't need to do any manual conversion to IEnumerable—it's ready to use out of the box.

Here's the function:

using System.Collections.Generic;
using System.Linq;

public IEnumerable<int> GetIntegerValues(List<object> objectList)
{
    // OfType<int> filters and casts in one step
    return objectList.OfType<int>();
}

What If You Need to Handle Convertible Values? #

If your list has elements that aren't strictly int but can be converted to one (like strings with numeric values, long values that fit in an int, etc.), you can use a more flexible approach with type checking and parsing:

using System.Collections.Generic;

public IEnumerable<int> GetConvertibleIntegerValues(List<object> objectList)
{
    foreach (var item in objectList)
    {
        // Check if the item is already an int
        if (item is int intValue)
        {
            yield return intValue;
        }
        // Try parsing string values to int
        else if (item is string strValue && int.TryParse(strValue, out int parsedInt))
        {
            yield return parsedInt;
        }
        // Convert long values that fit within int range
        else if (item is long longValue && longValue >= int.MinValue && longValue <= int.MaxValue)
        {
            yield return (int)longValue;
        }
        // Add more cases here if you need to handle other types (e.g., double)
    }
}

Why Your Previous Attempt Might Have Failed #

If you were trying to use Cast<int>() instead of OfType<int>(), that's likely the issue. Cast<int>() will throw an exception if it encounters an element that can't be cast directly to int, whereas OfType<int>() simply skips those elements. That's probably why your function wasn't running correctly.

Test It Out #

Here's how you can test these functions with a mixed list:

var mixedObjects = new List<object> { 42, "not a number", 99, "123", 1000L, 3.14 };

// Get only strict int values: returns 42, 99
var strictIntegers = GetIntegerValues(mixedObjects);

// Get all convertible values: returns 42, 99, 123, 1000
var allConvertibleIntegers = GetConvertibleIntegerValues(mixedObjects);

That should solve your problem! Let me know if you run into any specific edge cases you need help with.

内容的提问来源于stack exchange，提问作者Yaroslav Dokuzov