如何在 C# 中更新存储在字典中的值？
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How to update the value stored in Dictionary in C#?
提问by Amit
How to update value for a specific key in a dictionary Dictionary<string, int>?
如何更新字典中特定键的值Dictionary<string, int>？
采纳答案by ccalboni
Just point to the dictionary at given key and assign a new value:
只需指向给定键的字典并分配一个新值：
myDictionary[myKey] = myNewValue;
回答by Amit
It's possible by accessing the key as index
可以通过访问键作为索引
for example:
例如：
Dictionary<string, int> dictionary = new Dictionary<string, int>();
dictionary["test"] = 1;
dictionary["test"] += 1;
Console.WriteLine (dictionary["test"]); // will print 2
回答by Matthew
Here is a way to update by an index much like foo[x] = 9where xis a key and 9 is the value
这是一种通过索引更新的方法，就像foo[x] = 9where xis a key and 9 is the value
var views = new Dictionary<string, bool>();
foreach (var g in grantMasks)
{
string m = g.ToString();
for (int i = 0; i <= m.Length; i++)
{
views[views.ElementAt(i).Key] = m[i].Equals('1') ? true : false;
}
}
回答by max_force
You can follow this approach:
您可以遵循以下方法：
void addOrUpdate(Dictionary<int, int> dic, int key, int newValue)
{
int val;
if (dic.TryGetValue(key, out val))
{
// yay, value exists!
dic[key] = val + newValue;
}
else
{
// darn, lets add the value
dic.Add(key, newValue);
}
}
The edge you get here is that you check and get the value of corresponding key in just 1 access to the dictionary.
If you use ContainsKeyto check the existance and update the value using dic[key] = val + newValue;then you are accessing the dictionary twice.
您在这里获得的优势是，您只需 1 次访问字典即可检查并获取相应键的值。如果您ContainsKey用来检查存在性并使用更新值，dic[key] = val + newValue;那么您将访问字典两次。
回答by INT_24h
Use LINQ: Access to dictionary for the key and change the value
使用 LINQ：访问键的字典并更改值
Dictionary<string, int> dict = new Dictionary<string, int>();
dict = dict.ToDictionary(kvp => kvp.Key, kvp => kvp.Value + 1);
回答by Mister Pitt
This may work for you:
这可能对您有用：
Scenario 1: primitive types
场景 1：原始类型
string keyToMatchInDict = "x";
int newValToAdd = 1;
Dictionary<string,int> dictToUpdate = new Dictionary<string,int>{"x",1};
if(!dictToUpdate.ContainsKey(keyToMatchInDict))
dictToUpdate.Add(keyToMatchInDict ,newValToAdd );
else
dictToUpdate[keyToMatchInDict] = newValToAdd; //or you can do operations such as ...dictToUpdate[keyToMatchInDict] += newValToAdd;
Scenario 2: The approach I used for a List as Value
场景 2：我用于 List as Value 的方法
int keyToMatch = 1;
AnyObject objInValueListToAdd = new AnyObject("something for the Ctor")
Dictionary<int,List<AnyObject> dictToUpdate = new Dictionary<int,List<AnyObject>(); //imagine this dict got initialized before with valid Keys and Values...
if(!dictToUpdate.ContainsKey(keyToMatch))
dictToUpdate.Add(keyToMatch,new List<AnyObject>{objInValueListToAdd});
else
dictToUpdate[keyToMatch] = objInValueListToAdd;
Hope it's useful for someone in need of help.
希望对需要帮助的人有用。
回答by Vlad Kaponir
update- modify existent only. To avoid side effect of indexer use:
int val; if (dic.TryGetValue(key, out val)) { // key exist dic[key] = val; }update or (addnew if value doesn't exist in dic)
dic[key] = val;for instance:
d["Two"] = 2; // adds to dictionary because "two" not already present d["Two"] = 22; // updates dictionary because "two" is now present
更新- 仅修改现有。为避免索引器使用的副作用：
int val; if (dic.TryGetValue(key, out val)) { // key exist dic[key] = val; }更新或（如果 dic 中不存在值，则添加新的）
dic[key] = val;例如：
d["Two"] = 2; // adds to dictionary because "two" not already present d["Two"] = 22; // updates dictionary because "two" is now present
