บทความนี้สาธิตวิธีตรวจสอบว่า StringDictionary มีค่า (value) ที่ระบุอยู่หรือไม่ โดยใช้เมธอด ContainsValue() ใน C#
ตัวอย่างที่ 1: ตรวจสอบค่าและคีย์ใน StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
public class Demo
{
public static void Main()
{
StringDictionary strDict1 = new StringDictionary();
strDict1.Add("A", "John");
strDict1.Add("B", "Andy");
strDict1.Add("C", "Tim");
strDict1.Add("D", "Ryan");
strDict1.Add("E", "Kevin");
strDict1.Add("F", "Katie");
strDict1.Add("G", "Brad");
Console.WriteLine("StringDictionary1 elements...");
foreach (DictionaryEntry d in strDict1)
{
Console.WriteLine(d.Key + " " + d.Value);
}
Console.WriteLine("Does StringDictionary1 has key G? " + strDict1.ContainsKey("G"));
Console.WriteLine("Does StringDictionary1 has value Ryan? " + strDict1.ContainsValue("Ryan"));
StringDictionary strDict2 = new StringDictionary();
strDict2.Add("A", "John");
strDict2.Add("B", "Andy");
strDict2.Add("C", "Tim");
strDict2.Add("D", "Ryan");
strDict2.Add("E", "Kevin");
strDict2.Add("F", "Katie");
strDict2.Add("G", "Brad");
Console.WriteLine("\nStringDictionary2 elements...");
foreach (DictionaryEntry d in strDict2)
{
Console.WriteLine(d.Key + " " + d.Value);
}
Console.WriteLine("\nIs Dictionary2 equal to Dictionary1? = " + strDict2.Equals(strDict1));
Console.WriteLine("Does StringDictionary2 has key B? " + strDict2.ContainsKey("B"));
}
}
ผลลัพธ์
StringDictionary1 elements... a John b Andy c Tim d Ryan e Kevin f Katie g Brad Does StringDictionary1 has key G? True Does StringDictionary1 has value Ryan? True StringDictionary2 elements... a John b Andy c Tim d Ryan e Kevin f Katie g Brad Is Dictionary2 equal to Dictionary1? = False Does StringDictionary2 has key B? True
ตัวอย่างที่ 2: ตรวจสอบค่าที่ไม่มีอยู่ใน StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
public class Demo
{
public static void Main()
{
StringDictionary strDict1 = new StringDictionary();
strDict1.Add("U", "Electronics");
strDict1.Add("V", "Toys");
strDict1.Add("W", "Books");
strDict1.Add("X", "Accessories");
Console.WriteLine("StringDictionary1 elements...");
foreach (DictionaryEntry d in strDict1)
{
Console.WriteLine(d.Key + " " + d.Value);
}
Console.WriteLine("Does StringDictionary1 has key G? " + strDict1.ContainsKey("G"));
Console.WriteLine("Does StringDictionary1 has value Footwear? " + strDict1.ContainsValue("Footwear"));
StringDictionary strDict2 = new StringDictionary();
strDict2.Add("A", "John");
strDict2.Add("B", "Andy");
strDict2.Add("C", "Tim");
strDict2.Add("D", "Ryan");
strDict2.Add("E", "Kevin");
strDict2.Add("F", "Katie");
strDict2.Add("G", "Brad");
Console.WriteLine("\nStringDictionary2 elements...");
foreach (DictionaryEntry d in strDict2)
{
Console.WriteLine(d.Key + " " + d.Value);
}
Console.WriteLine("\nIs Dictionary2 equal to Dictionary1? = " + strDict2.Equals(strDict1));
Console.WriteLine("Does StringDictionary2 has key B? " + strDict2.ContainsKey("B"));
}
}
ผลลัพธ์
StringDictionary1 elements... x Accessories u Electronics v Toys w Books Does StringDictionary1 has key G? False Does StringDictionary1 has value Footwear? False StringDictionary2 elements... a John b Andy c Tim d Ryan e Kevin f Katie g Brad Is Dictionary2 equal to Dictionary1? = False Does StringDictionary2 has key B? True
สรุป
- ใช้
ContainsValue()เพื่อตรวจสอบว่ามีค่าที่ระบุอยู่ใน StringDictionary หรือไม่ - ใช้
ContainsKey()เพื่อตรวจสอบคีย์ - เมธอด
Equals()เปรียบเทียบอ้างอิงออบเจ็กต์ ไม่ใช่เนื้อหา ดังนั้นจึงคืนค่าFalseแม้ข้อมูลจะเหมือนกัน
