LINQ之OrderBy,OrderByDescending
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目录
- OrderBy()
- OrderByDescending()
OrderBy()
按升序对序列的元素进行排序。
MSDN
以下示例使用lambda表达式返回元素本身。
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
static void Main( string[] args )
{
int[] dataA = new int[] { 3, 1, 2, 0, 4 };
List<float> dataB = new List<float>() { 1.5f, 1.3f, 3.2f };
string[] dataC = new string[] { "正一郎", "清次郎", "誠三郎", "征史郎" };
IOrderedEnumerable<int> orderedDataA = dataA.OrderBy( value => value );
IOrderedEnumerable<float> orderedDataB = dataB.OrderBy( value => value );
IOrderedEnumerable<string> orderedDataC = dataC.OrderBy( value => value );
System.Console.WriteLine( "dataA :{0}", dataA.Text() );
System.Console.WriteLine( "dataA ordered:{0}", orderedDataA.Text() );
System.Console.WriteLine( "dataB :{0}", dataB.Text() );
System.Console.WriteLine( "dataB ordered:{0}", orderedDataB.Text() );
System.Console.WriteLine( "dataC :{0}", dataC.Text() );
System.Console.WriteLine( "dataC ordered:{0}", orderedDataC.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
dataA :[3], [1], [2], [0], [4],
dataA ordered:[0], [1], [2], [3], [4],
dataB :[1.5], [1.3], [3.2],
dataB ordered:[1.3], [1.5], [3.2],
dataC :[正一郎], [清次郎], [誠三郎], [征史郎],
dataC ordered:[征史郎], [正一郎], [清次郎], [誠三郎],
可以指定根据特定元素进行排列。
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
private class Parameter
{
public int ID { get; set; }
public string Name { get; set; }
public override string ToString()
{
return string.Format( "ID:{0}, Name:{1}", ID, Name );
}
}
static void Main( string[] args )
{
Parameter[] parameters = new Parameter[]
{
new Parameter() { ID = 0, Name = "正一郎" },
new Parameter() { ID = 3, Name = "清次郎" },
new Parameter() { ID = 2, Name = "誠三郎" },
new Parameter() { ID = 5, Name = "征史郎" },
};
IOrderedEnumerable<Parameter> orderedParameters = parameters.OrderBy( value => value.ID );
System.Console.WriteLine( "parameters :{0}", parameters.Text() );
System.Console.WriteLine( "parameters ordered:{0}", orderedParameters.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
parameters :[ID:0, Name:正一郎], [ID:3, Name:清次郎], [ID:2, Name:誠三郎], [ID:5, Name:征史郎],
parameters ordered:[ID:0, Name:正一郎], [ID:2, Name:誠三郎], [ID:3, Name:清次郎], [ID:5, Name:征史郎],
OrderByDescending()
您可以使用OrderByDescending()降序排序。
用法与OrderBy()相同。
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
static void Main( string[] args )
{
int[] dataA = new int[] { 3, 1, 2, 0, 4 };
List<float> dataB = new List<float>() { 1.5f, 1.3f, 3.2f };
string[] dataC = new string[] { "正一郎", "清次郎", "誠三郎", "征史郎" };
IOrderedEnumerable<int> orderedDataA = dataA.OrderByDescending( value => value );
IOrderedEnumerable<float> orderedDataB = dataB.OrderByDescending( value => value );
IOrderedEnumerable<string> orderedDataC = dataC.OrderByDescending( value => value );
System.Console.WriteLine( "dataA :{0}", dataA.Text() );
System.Console.WriteLine( "dataA ordered:{0}", orderedDataA.Text() );
System.Console.WriteLine( "dataB :{0}", dataB.Text() );
System.Console.WriteLine( "dataB ordered:{0}", orderedDataB.Text() );
System.Console.WriteLine( "dataC :{0}", dataC.Text() );
System.Console.WriteLine( "dataC ordered:{0}", orderedDataC.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
private class Parameter
{
public int ID { get; set; }
public string Name { get; set; }
public override string ToString()
{
return string.Format( "ID:{0}, Name:{1}", ID, Name );
}
}
static void Main( string[] args )
{
Parameter[] parameters = new Parameter[]
{
new Parameter() { ID = 0, Name = "正一郎" },
new Parameter() { ID = 3, Name = "清次郎" },
new Parameter() { ID = 2, Name = "誠三郎" },
new Parameter() { ID = 5, Name = "征史郎" },
};
IOrderedEnumerable<Parameter> orderedParameters = parameters.OrderByDescending( value => value.ID );
System.Console.WriteLine( "parameters :{0}", parameters.Text() );
System.Console.WriteLine( "parameters ordered:{0}", orderedParameters.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
parameters :[ID:0, Name:正一郎], [ID:3, Name:清次郎], [ID:2, Name:誠三郎], [ID:5, Name:征史郎],
parameters ordered:[ID:5, Name:征史郎], [ID:3, Name:清次郎], [ID:2, Name:誠三郎], [ID:0, Name:正一郎],
如果直接拿类进行比较呢？
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
private class Parameter
{
public int ID { get; set; }
public string Name { get; set; }
public override string ToString()
{
return string.Format( "ID:{0}, Name:{1}", ID, Name );
}
}
static void Main( string[] args )
{
Parameter[] parameters = new Parameter[]
{
new Parameter() { ID = 0, Name = "正一郎" },
new Parameter() { ID = 3, Name = "清次郎" },
new Parameter() { ID = 2, Name = "誠三郎" },
new Parameter() { ID = 5, Name = "征史郎" },
};
IOrderedEnumerable<Parameter> orderedParameters = parameters.OrderBy( value => value );
try
{
bool isAny = orderedParameters.Any();
}
catch( System.Exception i_exception )
{
System.Console.WriteLine( "{0}", i_exception );
System.Console.ReadKey();
return;
}
System.Console.WriteLine( "parameters :{0}", parameters.Text() );
System.Console.WriteLine( "parameters ordered:{0}", orderedParameters.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
System.ArgumentException：IComparable必须在至少一个对象上实现。
直接用类比较会报错。但是我们可以通过继承IComparable接口实现。
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
private class Parameter : System.IComparable<Parameter>
{
public int ID { get; set; }
public string Name { get; set; }
public int CompareTo( Parameter i_other )
{
if( i_other == null )
{
return -1;
}
return ID - i_other.ID;
}
public override string ToString()
{
return string.Format( "ID:{0}, Name:{1}", ID, Name );
}
}
static void Main( string[] args )
{
Parameter[] parameters = new Parameter[]
{
new Parameter() { ID = 0, Name = "正一郎" },
new Parameter() { ID = 3, Name = "清次郎" },
new Parameter() { ID = 2, Name = "誠三郎" },
new Parameter() { ID = 5, Name = "征史郎" },
};
IOrderedEnumerable<Parameter> ascendingParameters = parameters.OrderBy( value => value );
IOrderedEnumerable<Parameter> descendingParameters = parameters.OrderByDescending( value => value );
System.Console.WriteLine( "parameters :{0}", parameters.Text() );
System.Console.WriteLine( "parameters 昇順:{0}", ascendingParameters.Text() );
System.Console.WriteLine( "parameters 降順:{0}", descendingParameters.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
parameters :[ID:0, Name:正一郎], [ID:3, Name:清次郎], [ID:2, Name:誠三郎], [
ID:5, Name:征史郎],
parameters 昇順:[ID:0, Name:正一郎], [ID:2, Name:誠三郎], [ID:3, Name:清次郎], [
ID:5, Name:征史郎],
parameters 降順:[ID:5, Name:征史郎], [ID:3, Name:清次郎], [ID:2, Name:誠三郎], [
ID:0, Name:正一郎],
对于现有类型，我们也可以通过IComparer自定义排序规则。
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public static class Program
{
private class CompareInt : IComparer<int>
{
public int Compare( int i_lhs, int i_rhs )
{
bool isEvenNumberL = i_lhs % 2 == 0;
bool isEvenNumberR = i_rhs % 2 == 0;
if( isEvenNumberL && !isEvenNumberR )
{
return -1;
}
if( !isEvenNumberL && isEvenNumberR )
{
return 1;
}
return i_lhs - i_rhs;
}
}
static void Main( string[] args )
{
int[] numbers = new int[] { 3, 1, 2, 0, 4, 4, 7, 4, 8, 9 };
CompareInt compare = new CompareInt();
IOrderedEnumerable<int> ascendingNumbers = numbers.OrderBy( value => value, compare );
IOrderedEnumerable<int> descendingNumbers = numbers.OrderByDescending( value => value, compare );
System.Console.WriteLine( "numbers :{0}", numbers.Text() );
System.Console.WriteLine( "numbers 昇順:{0}", ascendingNumbers.Text() );
System.Console.WriteLine( "numbers 降順:{0}", descendingNumbers.Text() );
System.Console.ReadKey();
}
public static string Text( this IEnumerable i_source )
{
string text = string.Empty;
foreach( var value in i_source )
{
text += string.Format( "[{0}], ", value );
}
return text;
}
}
numbers :[3], [1], [2], [0], [4], [4], [7], [4], [8], [9],
numbers 昇順:[0], [2], [4], [4], [4], [8], [1], [3], [7], [9],
numbers 降順:[9], [7], [3], [1], [8], [4], [4], [4], [2], [0],