Seven Common Uses of Dictionary Generic Set in C
- 2021-09-20 21:19:22
- OfStack
To use the Dictionary collection, you need to import the C # generic namespace
System. Collections. Generic (Assembly: mscorlib)
Description of Dictionary
1. Mapping from 1 set of keys (Key) to 1 set of values (Value), where each addition consists of a value and its associated key
2. Any key must be 1-only
3. The key cannot be a null reference null (Nothing in VB). If the value is a reference type, it can be a null value
4. Key and Value can be of any type (string, int, custom, class, etc.)
Common usage of Dictionary: Take the type of key as int and the type of value as string as an example
1. Create and initialize
Dictionary<int,string>myDictionary=newDictionary<int,string>();
2. Add Elements
myDictionary.Add(1,"C#");
myDictionary.Add(2,"C++");
myDictionary.Add(3,"ASP.NET");
myDictionary.Add(4,"MVC");
3. Find elements through Key
if(myDictionary.ContainsKey(1))
{
Console.WriteLine("Key:{0},Value:{1}","1", myDictionary[1]);
}
4. Traverse elements through KeyValuePair
foreach(KeyValuePair<int,string>kvp in myDictionary)
{
Console.WriteLine("Key = {0}, Value = {1}",kvp.Key, kvp.Value);
}
5. Only traverse the key Keys property
Dictionary<int,string>.KeyCollection keyCol=myDictionary.Keys;
foreach(intkeyinkeyCol)
{
Console.WriteLine("Key = {0}", key);
}
6. Only the value Valus property is traversed
Dictionary<int,string>.ValueCollection valueCol=myDictionary.Values;
foreach(stringvalueinvalueCol)
{
Console.WriteLine("Value = {0}", value);
}
7. Remove the specified key value by Remove method
myDictionary.Remove(1);
if(myDictionary.ContainsKey(1))
{
Console.WriteLine("Key:{0},Value:{1}","1", myDictionary[1]);
}
else
{
Console.WriteLine(" Nonexistent Key : 1");
}
Description of other common properties and methods:
Comparer: | 获取用于确定字典中的键是否相等的 IEqualityComparer。 |
Count: | 获取包含在 Dictionary中的键/值对的数目。 |
Item: | 获取或设置与指定的键相关联的值。 |
Keys: | 获取包含 Dictionary中的键的集合。 |
Values: | 获取包含 Dictionary中的值的集合。 |
Add: | 将指定的键和值添加到字典中。 |
Clear: | 从 Dictionary中移除所有的键和值。 |
ContainsKey: | 确定 Dictionary是否包含指定的键。 |
ContainsValue: | 确定 Dictionary是否包含特定值。 |
GetEnumerator: | 返回循环访问 Dictionary的枚举数。 |
GetType: | 获取当前实例的 Type。 (从 Object 继承。) |
Remove: | 从 Dictionary中移除所指定的键的值。 |
ToString: | 返回表示当前 Object的 String。 (从 Object 继承。) |
TryGetValue: | 获取与指定的键相关联的值。 |