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[英]Storing a Dictionary<int,string> or KeyValuePair in a database
[英]Convert an IOrderedEnumerable<KeyValuePair<string, int>> into a Dictionary<string, int>
// itemCounter is a Dictionary<string, int>, and I only want to keep
// key/value pairs with the top maxAllowed values
if (itemCounter.Count > maxAllowed) {
IEnumerable<KeyValuePair<string, int>> sortedDict =
from entry in itemCounter orderby entry.Value descending select entry;
sortedDict = sortedDict.Take(maxAllowed);
itemCounter = sortedDict.ToDictionary<string, int>(/* what do I do here? */);
}
Visual Studio要求参数Func<string, int> keySelector
。 我尝试了一些我在网上找到的半相关示例并放入k => k.Key
,但这会产生编译错误:
'System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string,int>>'
不包含'ToDictionary'的定义和最佳扩展方法重载'System.Linq.Enumerable.ToDictionary<TSource,TKey>(System.Collections.Generic.IEnumerable<TSource>, System.Func<TSource,TKey>)'
有一些无效的参数
您正在指定不正确的通用参数。 你说TSource是字符串,实际上它是KeyValuePair。
这个是正确的:
sortedDict.ToDictionary<KeyValuePair<string, int>, string, int>(pair => pair.Key, pair => pair.Value);
短版本是:
sortedDict.ToDictionary(pair => pair.Key, pair => pair.Value);
我相信最简洁的方法:将字典排序并将其转换回字典将是:
itemCounter = itemCounter.OrderBy(i => i.Value).ToDictionary(i => i.Key, i => i.Value);
这个问题太旧了,但还是想给出答案供参考:
itemCounter = itemCounter.Take(maxAllowed).OrderByDescending(i => i.Value).ToDictionary(i => i.Key, i => i.Value);
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