C# 创建匿名LINQ Lambda排序表达式
如何创建一个基于MyObject属性的sortExpression通用方法,如下所示:C# 创建匿名LINQ Lambda排序表达式,c#,linq,lambda,C#,Linq,Lambda,如何创建一个基于MyObject属性的sortExpression通用方法,如下所示: void CreateSortedReport(IList<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true) { //sort the [list] by sortExpression and by direction; } 或 编辑1
void CreateSortedReport(IList<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true)
{
//sort the [list] by sortExpression and by direction;
}
或
编辑1:
我之所以要求使用泛型方法,是因为有些方法非常相似:
CreateReportSortedByName(myItems) {
return myItems.OrderBy(x=>x.Name);
}
CreateReportSortedByDate(myItems) {
return myItems.OrderBy(x=>x.CreateDate);
}
假设
MyObject
是一个具体类型,只需向方法签名添加一个泛型参数(
):
void CreateReport<TSort>(IList<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true)
假设
MyObject
是一个具体类型,只需向方法签名添加一个泛型参数(
):
void CreateReport<TSort>(IList<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true)
要使用内置排序函数提供就地排序,您需要编写一个实现
IComparer
的类
例如:
class CompareWithDelegate<TOnObject, TSort> : IComparer<TOnObject>
{
Func<TOnObject, TSort> evaluator;
IComparer comparer = Comparer.Default;
bool ascending;
public CompareWithDelegate(Expression<Func<TOnObject, TSort>> expr, bool ascending = true)
{
evaluator = expr.Compile();
this.ascending = ascending;
}
public int Compare(TOnObject left, TOnObject right)
{
var leftVal = evaluator(left);
var rightVal = evaluator(right);
return (ascending ? 1 : -1) * comparer.Compare(leftVal, rightVal);
}
}
或者动态编译表达式:
void CreateSortedReport<TSort>(List<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true)
{
var method = sortExpression.Compile();
var t =
ascending
? list.OrderBy (method)
: list.OrderByDescending(method);
}
void CreateSortedReport(列表,表达式sortExpression,bool升序=true)
{
var method=sortExpression.Compile();
变量t=
提升
?list.OrderBy(方法)
:list.OrderByDescending(方法);
}
要使用内置排序函数提供就地排序,您需要编写一个实现IComparer
的类
例如:
class CompareWithDelegate<TOnObject, TSort> : IComparer<TOnObject>
{
Func<TOnObject, TSort> evaluator;
IComparer comparer = Comparer.Default;
bool ascending;
public CompareWithDelegate(Expression<Func<TOnObject, TSort>> expr, bool ascending = true)
{
evaluator = expr.Compile();
this.ascending = ascending;
}
public int Compare(TOnObject left, TOnObject right)
{
var leftVal = evaluator(left);
var rightVal = evaluator(right);
return (ascending ? 1 : -1) * comparer.Compare(leftVal, rightVal);
}
}
或者动态编译表达式:
void CreateSortedReport<TSort>(List<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true)
{
var method = sortExpression.Compile();
var t =
ascending
? list.OrderBy (method)
: list.OrderByDescending(method);
}
void CreateSortedReport(列表,表达式sortExpression,bool升序=true)
{
var method=sortExpression.Compile();
变量t=
提升
?list.OrderBy(方法)
:list.OrderByDescending(方法);
}
您可以基于内置函数构建扩展方法
您可以基于内置函数构建扩展方法
@DioPhung,如果你在
IList
上操作,你可以用Func
@sstan替换你的表达式monad:没错,我想在方法内部进行就地排序。@DioPhung,如果你在IList
上操作,你可以用Func
替换你的表达式monad@sstan:没错,我想在方法内部进行就地排序。
void CreateSortedReport<TSort>(List<MyObject> list, Func<MyObject, TSort> sortExpression, bool ascending = true)
{
var t =
ascending
? list.OrderBy (sortExpression)
: list.OrderByDescending(sortExpression);
}
void CreateSortedReport<TSort>(List<MyObject> list, Expression<Func<MyObject, TSort>> sortExpression, bool ascending = true)
{
var method = sortExpression.Compile();
var t =
ascending
? list.OrderBy (method)
: list.OrderByDescending(method);
}
public static class SortExtension
{
public static void SortBy<T, TProperty>(this List<T> list, Func<T, TProperty> orderby, bool ascending = true)
{
list.Sort(new InnerComparer<T, TProperty>(orderby, ascending));
}
class InnerComparer<T, TProperty> : IComparer<T>
{
private readonly Func<T, TProperty> _property;
private readonly int _ascending;
public InnerComparer(Func<T, TProperty> property, bool ascending)
{
_property = property;
_ascending = ascending ? 1 : -1;
}
int IComparer<T>.Compare(T x, T y)
{
var p1 = _property(x);
var p2 = _property(y);
return _ascending * Comparer<TProperty>.Default.Compare(p1, p2);
}
}
}
myObjects.SortBy(o => o.MyProperty);