Csharp/CSharp Tutorial/String/String Compare
Содержание
- 1 Compare for equal
- 2 Compare string case sensitively
- 3 Compare string: equal, less than or greater than
- 4 Compare strings using StringComparison enumeration: InvariantCulture
- 5 Compare string with start index and end index
- 6 Compare string with String.Compare(string str1, strng str2)
- 7 If two string are equal
- 8 String comparisons: ignore case
- 9 String equality
- 10 String Interning
- 11 Use "==" to compare two string objects
Compare for equal
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string str1 = "ABCDEabcde1234567890";
string str2 = string.Copy(str1);
string str3 = "asdf";
// compare strings
if(str1 == str2)
Console.WriteLine("str1 == str2");
else
Console.WriteLine("str1 != str2");
if(str1 == str3)
Console.WriteLine("str1 == str3");
else
Console.WriteLine("str1 != str3");
}
}</source>
str1 == str2 str1 != str3
Compare string case sensitively
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string str1 = "one";
string str2 = "ONE";
if(String.rupare(str1, str2, true) == 0)
Console.WriteLine(str1 + " and " + str2 +
" are equal ignoring case.");
else
Console.WriteLine(str1 + " and " + str2 +
" are not equal ignoring case.");
}
}</source>
one and ONE are equal ignoring case.
Compare string: equal, less than or greater than
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string str1 = "ABCDEabcde1234567890";
string str3 = "C# strings are powerful.";
int result = str1.rupareTo(str3);
if(result == 0)
Console.WriteLine("str1 and str3 are equal");
else if(result < 0)
Console.WriteLine("str1 is less than str3");
else
Console.WriteLine("str1 is greater than str3");
}
}</source>
str1 is less than str3
Compare strings using StringComparison enumeration: InvariantCulture
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string pswd = "asdf";
string str = "fda";
// Compare using invariant culture.
if(String.rupare(pswd, str,
StringComparison.InvariantCulture) == 0)
Console.WriteLine("Password accepted.");
else
Console.WriteLine("Password invalid.");
}
}</source>
Password invalid.
Compare string with start index and end index
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string str1 = "one";
string str2 = "one, too";
if(String.rupare(str1, 0, str2, 0, 3) == 0)
Console.WriteLine("First part of " + str1 + " and " +
str2 + " are equal.");
else
Console.WriteLine("First part of " + str2 + " and " +
str2 + " are not equal.");
}
}</source>
First part of one and one, too are equal.
Compare string with String.Compare(string str1, strng str2)
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string str1 = "one";
string str2 = "two";
int result = String.rupare(str1, str2);
if(result < 0)
Console.WriteLine(str1 + " is less than " + str2);
else if(result > 0)
Console.WriteLine(str1 + " is greater than " + str2);
else
Console.WriteLine(str1 + " equals " + str2);
}
}</source>
one is less than two
If two string are equal
<source lang="csharp">using System;
class MainClass {
public static void Main() {
string str1 = "one";
string str2 = "one";
if(String.rupare(str1, str2) == 0)
Console.WriteLine(str1 + " and " + str2 +
" are equal.");
else
Console.WriteLine(str1 + " and " + str2 +
" are not equal.");
}
}</source>
one and one are equal.
String comparisons: ignore case
<source lang="csharp">using System; using System.Collections.Generic; using System.Globalization; using System.IO; using System.Text; public class MainClass {
public static void Main()
{
bool b1 = "hello" == "hello";
Console.WriteLine(b1);
bool b2 = "hello" == "hi";
Console.WriteLine(b2);
bool b3 = "hello".Equals("hello");
Console.WriteLine(b3);
bool b4 = "hello".Equals("hi");
Console.WriteLine(b4);
bool b5 = "HoWdY".Equals("howdy");
Console.WriteLine(b5);
bool b6 = "HoWdY".Equals("howdy", StringComparison.OrdinalIgnoreCase);
Console.WriteLine(b6);
}
}</source>
True False True False False True
String equality
<source lang="csharp">using System; using System.Collections.Generic; using System.Text;
class Program
{
static void Main(string[] args)
{
string s1 = "Hello!";
string s2 = "Yo!";
Console.WriteLine("s1 = {0}", s1);
Console.WriteLine("s2 = {0}", s2);
Console.WriteLine();
Console.WriteLine("s1 == s2: {0}", s1 == s2);
Console.WriteLine("s1 == Hello!: {0}", s1 == "Hello!");
Console.WriteLine("s1 == HELLO!: {0}", s1 == "HELLO!");
Console.WriteLine("s1 == hello!: {0}", s1 == "hello!");
Console.WriteLine("s1.Equals(s2): {0}", s1.Equals(s2));
Console.WriteLine("Yo.Equals(s2): {0}", "Yo!".Equals(s2));
}
}</source>
String Interning
<source lang="csharp">using System; class MainClass {
public static void Main()
{
string s1 = "Hello";
string s2 = "Hello";
string s3 = "Hello".Substring(0, 4) + "o";
Console.WriteLine("Str == : {0}", s1 == s2);
Console.WriteLine("Ref == : {0}", (object) s1 == (object) s2);
Console.WriteLine("Str == : {0}", s1 == s3);
Console.WriteLine("Ref == : {0}", (object) s1 == (object) s3);
}
}</source>
Str == : True Ref == : True Str == : True Ref == : False
Use "==" to compare two string objects
<source lang="csharp">using System; class MainClass {
public static void Main()
{
string test1 = "This is a test string";
string test2, test3;
test2 = test1.Insert(15, "AAA ");
test3 = test1.ToUpper();
Console.WriteLine("test1: "{0}"", test1);
Console.WriteLine("test2: "{0}"", test2);
Console.WriteLine("test3: "{0}"", test3);
if (test1 == test3)
Console.WriteLine("test1 is equal to test3");
else
Console.WriteLine("test1 is not equal to test3");
}
}</source>
test1: "This is a test string" test2: "This is a test AAA string" test3: "THIS IS A TEST STRING" test1 is not equal to test3
