使用键获取存储在字典中的对象 [英] Get Object stored in Dictionary using key

问题描述

我正在使用Dictionary对象(C#)存储键(字符串)和值(对象)对.

I'm using a Dictionary object (C#) to store key (string) and value (Object) pairs.

我能够毫无问题地将对象存储在字典中.但是，访问它们对我不起作用.

I am able to store the Objects in the dictionary without a problem. However, accessing them is not working for me.

这是我想出的代码:

Object con;

if (dict.ContainsKey(theKey))
{
     con = dict.FirstOrDefault(x => x.Value == theKey).Key;
}
else
{
     throw new Exception("Connection instance unavailable : " + theKey);
}

由于某些原因，con始终返回空.

For some reason, con always returns empty.

推荐答案

使用此:

if (dict.ContainsKey(theKey))
{
     con = dict[theKey];
}

这是LinqPad的小脚本:

Here is a little script for LinqPad:

var dictionary = new Dictionary<String, Object>();

dictionary.Add("myKey", new Object());

var myKey = "myKey";
Object con;
if (dictionary.ContainsKey(myKey))
{
    con = dictionary[myKey];
    // con is populated
}

此外，您还可以在 DotnetFiddle

根据Matthew Watson的评论，使用以下方法比ContainsKey更有效:

As per comments from Matthew Watson, using the following method is more efficient than ContainsKey:

if (dictionary.TryGetValue(myKey, out con))
{
    // con is populated again
}

此代码执行一次搜索，而ContainsKey和[]进行两次搜索.

This code conducts search once, where as ContainsKey and [] does search twice.

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