在C#中,Dictionary 是根据键(Key)来快速查找值(Value)的数据结构。然而,如果你需要根据值来查找键,Dictionary 本身并不直接支持这种操作。不过,你可以通过一些额外的方法来实现这一需求。以下是一个详细的步骤和代码示例,展示了如何在C#中根据值来查找键: 创建一个C#字典并填充数据: csharp using System; using ...
Python dictionaries can also be created using the dict() constructor by simply providing a list or tuple of comma-separated key-value pairs. This constructor keeps track of the insertion order of key-value pairs in the dictionary. Before Python 3.6, we used to rely on OrderedDict class of th...
If the key is there in the dictionary, it returns the existing value. This method is convenient when you might want to aggregate things or perform counting without checking whether a key exists before incrementing an associated value. Also, you will use list comprehension to find all the dupli...
stringkeyToFind="brown"; varresult=MyDictionary.FirstOrDefault(x=>x.Key==keyToFind); if(result.Equals(default(KeyValuePair))) { Console.WriteLine($"The key '{keyToFind}' does not exist in the dictionary."); } else { Console.WriteLine($"The value associated with the key '{keyToFind...
The Dictionary<TKey,TValue> generic class provides a mapping from a set of keys to a set of values. Each addition to the dictionary consists of a value and its associated key. Retrieving a value by using its key is very fast, close to O(1), because the Dictionary<TKey,TValue> ...
ListDictionary<TKey,TValue>.FindAllValuesByKey MethodReference Feedback DefinitionNamespace: Microsoft.Practices.CompositeUI.Utility Assembly: Microsoft.Uii.Practices.CompositeUI.dll C# 複製 public System.Collections.Generic.IEnumerable<TValue> FindAllValuesByKey (Predicate<TKey> keyFilter); ...
从源码中看到 ContainsKey 是一个查找Key位置的过程。它调用了 FindEntry 函数,FindEntry 查找Key值位置的方法跟我们前面提到的相同。从用Key值得到的哈希值地址开始查找,查看所有冲突链表中,是否有与Key值相同的值,找到即刻返回该索引地址。 有了前面对几个核心接口理解的基础,其他接口相对比较就简单多了,我们快速的...
If the target value matches with some of the items in the dict object, then we’ll add the key to a temp list. Using For Loop Let’s go through the below sample program that uses a for loop. It defines a searchKeysByVal() function to search for keys in the dictionary of Fortune ...
Inside the Dictionary.Here's what the above code looks like in memory. The Dictionary instance is represented by a collection of key and value pairs. The screenshot is worth looking at. Look up values Here we see how you can check to see if a given string is present in a Dictionary wi...
value = default(TValue); return false; } 于是,上面的代码就可以改写成: Dictionary<Key, Value> dict = new Dictionary<Key, Value>(); ... Value value; if (dict.TryGetValue(key, out value)) { value... } 使用TryGetValue,FindEntry 只调用了一次,同时判断了有没有也得到了值。在程序中常...