C# 使用 for 循环遍历字典
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using a for loop to iterate through a dictionary
提问by Arianule
I generally use a foreach loop to iterate through Dictionary.
我通常使用 foreach 循环来遍历 Dictionary。
Dictionary<string, string> dictSummary = new Dictionary<string, string>();
In this case I want to trim the entries of white space and the foreach loop does however not allow for this.
在这种情况下，我想修剪空白条目，但是 foreach 循环不允许这样做。
foreach (var kvp in dictSummary)
{
kvp.Value = kvp.Value.Trim();
}
How can I do this with a for loop?
我怎样才能用 for 循环做到这一点？
for (int i = dictSummary.Count - 1; i >= 0; i--)
{
}
采纳答案by Daniel Hilgarth
KeyValuePair<TKey, TValue>doesn't allow you to set the Value, it is immutable.
KeyValuePair<TKey, TValue>不允许您设置Value，它是不可变的。
You will have to do it like this:
你必须这样做：
foreach(var kvp in dictSummary.ToArray())
dictSummary[kvp.Key] = kvp.Value.Trim();
The important part here is the ToArray. That will copy the Dictionary into an array, so changing the dictionary inside the foreach will not throw an InvalidOperationException.
这里的重要部分是ToArray. 这会将 Dictionary 复制到一个数组中，因此更改 foreach 中的字典不会抛出InvalidOperationException.
An alternative approach would use LINQ's ToDictionarymethod:
另一种方法是使用 LINQ 的ToDictionary方法：
dictSummary = dictSummary.ToDictionary(x => x.Key, x => x.Value.Trim());
回答by Abdul Ahad
what about this?
那这个呢？
for (int i = dictSummary.Count - 1; i >= 0; i--) {
var item = dictSummary.ElementAt(i);
var itemKey = item.Key;
var itemValue = item.Value;
}
回答by Moslem Ben Dhaou
You don't need to use .ToArray()or .ElementAt(). It is as simple as accessing the dictionary with the key:
您不需要使用.ToArray()或.ElementAt()。它就像使用键访问字典一样简单：
dictSummary.Keys.ToList().ForEach(k => dictSummary[k] = dictSummary[k].Trim());
