Csharp/CSharp Tutorial/LINQ/ToDictionary
Содержание
Calling the First ToDictionary Prototype
<source lang="csharp">using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee {
public int id;
public string firstName;
public string lastName;
public static ArrayList GetEmployeesArrayList() {
ArrayList al = new ArrayList();
al.Add(new Employee { id = 1, firstName = "J", lastName = "R" });
al.Add(new Employee { id = 2, firstName = "W", lastName = "G" });
al.Add(new Employee { id = 3, firstName = "A", lastName = "H" });
al.Add(new Employee { id = 4, firstName = "D", lastName = "L" });
al.Add(new Employee { id = 101, firstName = "K", lastName = "F" });
return (al);
}
public static Employee[] GetEmployeesArray() {
return ((Employee[])GetEmployeesArrayList().ToArray());
}
} public class MainClass {
public static void Main() {
Dictionary<int, Employee> eDictionary = Employee.GetEmployeesArray().ToDictionary(k => k.id);
Employee e = eDictionary[2];
Console.WriteLine("Employee whose id == 2 is {0} {1}", e.firstName, e.lastName);
}
}</source>
Convert query to Dictionary
<source lang="csharp">using System; using System.Collections; using System.Collections.Generic; using System.Text; using System.Linq; public class MainClass{
public static void Main(){
var q = from m in typeof(int).GetMethods()
group m by m.Name into gb
select gb;
Dictionary<string, int> d = q.ToDictionary(k => k.Key, k => k.Count());
}
}</source>
Second ToDictionary
<source lang="csharp">using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee2 {
public string id;
public string firstName;
public string lastName;
public static ArrayList GetEmployeesArrayList() {
ArrayList al = new ArrayList();
al.Add(new Employee2 { id = "1", firstName = "J", lastName = "R" });
al.Add(new Employee2 { id = "2", firstName = "W", lastName = "G" });
al.Add(new Employee2 { id = "3", firstName = "A",lastName = "H"});
al.Add(new Employee2 { id = "4", firstName = "D", lastName = "L" });
al.Add(new Employee2 { id = "101", firstName = "K", lastName = "F" });
return (al);
}
public static Employee2[] GetEmployeesArray() {
return ((Employee2[])GetEmployeesArrayList().ToArray(typeof(Employee2)));
}
} public class MyStringifiedNumberComparer : IEqualityComparer<string> {
public bool Equals(string x, string y) {
return (Int32.Parse(x) == Int32.Parse(y));
}
public int GetHashCode(string obj) {
return Int32.Parse(obj).ToString().GetHashCode();
}
} public class MainClass {
public static void Main() {
Dictionary<string, Employee2> eDictionary = Employee2.GetEmployeesArray().ToDictionary(k => k.id, new MyStringifiedNumberComparer());
Employee2 e = eDictionary["2"];
Console.WriteLine("Employee whose id == \"2\" : {0} {1}", e.firstName, e.lastName);
e = eDictionary["000002"];
Console.WriteLine("Employee whose id == \"000002\" : {0} {1}",e.firstName, e.lastName);
}
}</source>
ToDictionary: convert query result to Dictionary
<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text; public class MainClass {
public static void Main() {
var scoreRecords = new[] { new {Name = "A", Score = 50},
new {Name = "B" , Score = 40},
new {Name = "C", Score = 45}
};
var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name);
Console.WriteLine("Bob"s score: {0}", scoreRecordsDict["Bob"]);
}
}</source>
ToDictionary for an object list
<source lang="csharp">using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee {
public int id;
public string firstName;
public string lastName;
public static ArrayList GetEmployeesArrayList() {
ArrayList al = new ArrayList();
al.Add(new Employee { id = 1, firstName = "J", lastName = "R" });
al.Add(new Employee { id = 2, firstName = "W", lastName = "G" });
al.Add(new Employee { id = 3, firstName = "A", lastName = "H" });
al.Add(new Employee { id = 4, firstName = "D", lastName = "L" });
al.Add(new Employee { id = 101, firstName = "K", lastName = "F" });
return (al);
}
public static Employee[] GetEmployeesArray() {
return ((Employee[])GetEmployeesArrayList().ToArray());
}
} public class MainClass {
public static void Main() {
Dictionary<int, string> eDictionary = Employee.GetEmployeesArray().ToDictionary(k => k.id, i => string.Format("{0} {1}",i.firstName, i.lastName));
string name = eDictionary[2];
Console.WriteLine("Employee whose id == 2 is {0}", name);
}
}</source>
ToDictionary with IEqualityComparer
<source lang="csharp">using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee2 {
public string id;
public string firstName;
public string lastName;
public static ArrayList GetEmployeesArrayList() {
ArrayList al = new ArrayList();
al.Add(new Employee2 { id = "1", firstName = "J", lastName = "R" });
al.Add(new Employee2 { id = "2", firstName = "W", lastName = "G" });
al.Add(new Employee2 { id = "3", firstName = "A", lastName = "H"});
al.Add(new Employee2 { id = "4", firstName = "D", lastName = "L" });
al.Add(new Employee2 { id = "101", firstName = "K", lastName = "F" });
return (al);
}
public static Employee2[] GetEmployeesArray() {
return ((Employee2[])GetEmployeesArrayList().ToArray(typeof(Employee2)));
}
} public class MyStringifiedNumberComparer : IEqualityComparer<string> {
public bool Equals(string x, string y) {
return (Int32.Parse(x) == Int32.Parse(y));
}
public int GetHashCode(string obj) {
return Int32.Parse(obj).ToString().GetHashCode();
}
} public class MainClass {
public static void Main() {
Dictionary<string, string> eDictionary = Employee2.GetEmployeesArray()
.ToDictionary(k => k.id,i => string.Format("{0} {1}",i.firstName, i.lastName),new MyStringifiedNumberComparer());
string name = eDictionary["2"];
Console.WriteLine("Employee whose id == \"2\" : {0}", name);
name = eDictionary["000002"];
Console.WriteLine("Employee whose id == \"000002\" : {0}", name);
}
}</source>
