LINQ之OrderBy,OrderByDescending

2024-01-09 06:19| 来源: 网络整理| 查看: 265

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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。

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 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 dataB = new List() { 1.5f, 1.3f, 3.2f }; string[] dataC = new string[] { "正一郎", "清次郎", "誠三郎", "征史郎" }; IOrderedEnumerable orderedDataA = dataA.OrderByDescending( value => value ); IOrderedEnumerable orderedDataB = dataB.OrderByDescending( value => value ); IOrderedEnumerable 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 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 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 { 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 ascendingParameters = parameters.OrderBy( value => value ); IOrderedEnumerable 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 { 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 ascendingNumbers = numbers.OrderBy( value => value, compare ); IOrderedEnumerable 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],

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