SoFunction
Updated on 2025-03-07

7 common usages of Dictionary generic collections in C#

To use Dictionary collection, you need to import the C# generic namespace

(Assembly: mscorlib)

Description of Dictionary
1. Mapping from a set of keys to a set of values ​​(Values), each added item is composed of a value and its associated keys.

2. Any key must be unique

3. The key cannot be null referenced null (Nothing in VB). If the value is a reference type, it can be null.

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. Creation and initialization

 

Copy the codeThe code is as follows:
Dictionary<int,string>myDictionary=newDictionary<int,string>();

2. Add elements

Copy the codeThe code is as follows:
(1,"C#");
(2,"C++");
(3,"");
(4,"MVC");

3. Find elements through Key

Copy the codeThe code is as follows:
if((1))
{
("Key:{0},Value:{1}","1", myDictionary[1]);
}

4. Traverse elements through KeyValuePair

Copy the codeThe code is as follows:
foreach(KeyValuePair<int,string>kvp in myDictionary)
{
("Key = {0}, Value = {1}",, );
}

5. Only traverse the keys attributes

Copy the codeThe code is as follows:
Dictionary<int,string>.KeyCollection keyCol=;
foreach(intkeyinkeyCol)
{
("Key = {0}", key);
}

6. Only traverse the value Valus attribute

Copy the codeThe code is as follows:
Dictionary<int,string>.ValueCollection valueCol=;
foreach(stringvalueinvalueCol)
{
("Value = {0}", value);
}

7. Remove the specified key value through the Remove method

Copy the codeThe code is as follows:
(1);
if((1))
{
("Key:{0},Value:{1}","1", myDictionary[1]);
}
else
{
("No Key : 1");
}

Description of other common properties and methods:

Comparer： Gets the IEqualityComparer used to determine whether the keys in the dictionary are equal.
Count： Gets the number of key/value pairs contained in Dictionary.
Item： Gets or sets the value associated with the specified key.
Keys： Gets a collection containing keys in Dictionary.
Values： Gets a collection containing values ​​in Dictionary.
Add： Adds the specified key and value to the dictionary.
Clear： Remove all keys and values ​​from Dictionary.
ContainsKey： Determines whether Dictionary contains the specified key.
ContainsValue： Determines whether Dictionary contains a specific value.
GetEnumerator： Returns the enumeration number that loops through the Dictionary.
GetType： Gets the Type of the current instance. (Inherited from Object.)
Remove： Removes the value of the specified key from the Dictionary.
ToString： Returns the String representing the current Object. (Inherited from Object.)
TryGetValue： Gets the value associated with the specified key.