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HT.Cloud.Code/Extend/Ext.Linq.cs
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211
HT.Cloud.Code/Extend/Ext.Linq.cs
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/*******************************************************************************
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* Copyright © 2016 HT.Cloud.Framework 版权所有
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* Author: HT.Cloud
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* Description: WaterCloud快速开发平台
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* Website：
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*********************************************************************************/
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using System;
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using System.Collections.Generic;
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using System.Data.SqlClient;
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using System.Linq;
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using System.Linq.Expressions;
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using System.Reflection;
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namespace HT.Cloud.Code
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{
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public static partial class ExtLinq
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{
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public static Expression Property(this Expression expression, string propertyName)
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{
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return Expression.Property(expression, propertyName);
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}
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public static Expression AndAlso(this Expression left, Expression right)
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{
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return Expression.AndAlso(left, right);
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}
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public static Expression OrElse(this Expression left, Expression right)
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{
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return Expression.OrElse(left, right);
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}
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public static Expression Call(this Expression instance, string methodName, params Expression[] arguments)
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{
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return Expression.Call(instance, instance.Type.GetMethod(methodName), arguments);
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}
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public static Expression GreaterThan(this Expression left, Expression right)
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{
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return Expression.GreaterThan(left, right);
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}
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public static Expression<T> ToLambda<T>(this Expression body, params ParameterExpression[] parameters)
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{
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return Expression.Lambda<T>(body, parameters);
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}
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public static Expression<Func<T, bool>> True<T>()
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{ return param => true; }
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public static Expression<Func<T, bool>> False<T>()
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{ return param => false; }
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public static Expression<Func<T, bool>> AndAlso<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
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{
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return first.Compose(second, Expression.AndAlso);
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}
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public static Expression<Func<T, bool>> OrElse<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
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{
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return first.Compose(second, Expression.OrElse);
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}
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public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
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{
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var map = first.Parameters
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.Select((f, i) => new { f, s = second.Parameters[i] })
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.ToDictionary(p => p.s, p => p.f);
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var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);
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return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
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}
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private class ParameterRebinder : ExpressionVisitor
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{
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private readonly Dictionary<ParameterExpression, ParameterExpression> map;
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/// <summary>
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/// Initializes a new instance of the <see cref="ParameterRebinder"/> class.
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/// </summary>
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/// <param name="map">The map.</param>
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private ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
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{
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this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
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}
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/// <summary>
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/// Replaces the parameters.
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/// </summary>
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/// <param name="map">The map.</param>
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/// <param name="exp">The exp.</param>
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/// <returns>Expression</returns>
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public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
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{
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return new ParameterRebinder(map).Visit(exp);
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}
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protected override Expression VisitParameter(ParameterExpression p)
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{
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ParameterExpression replacement;
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if (map.TryGetValue(p, out replacement))
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{
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p = replacement;
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}
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return base.VisitParameter(p);
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}
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}
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public static ParameterExpression CreateLambdaParam<T>(string name)
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{
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return Expression.Parameter(typeof(T), name);
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}
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/// <summary>
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/// 创建完整的lambda
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/// </summary>
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public static LambdaExpression GenerateLambda(this ParameterExpression param, Expression body)
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{
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//c=>c.XXX=="XXX"
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return Expression.Lambda(body, param);
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}
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public static Expression<Func<T, bool>> GenerateTypeLambda<T>(this ParameterExpression param, Expression body)
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{
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return (Expression<Func<T, bool>>)(param.GenerateLambda(body));
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}
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public static Expression Or(this Expression expression, Expression expressionRight)
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{
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return Expression.Or(expression, expressionRight);
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}
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public static Expression And(this Expression expression, Expression expressionRight)
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{
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return Expression.And(expression, expressionRight);
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}
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public static IOrderedQueryable<TEntity> SortBy<TEntity>(this IQueryable<TEntity> query, Expression<Func<TEntity, dynamic>> sortPredicate)
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where TEntity : class, new()
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{
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return InvokeSortBy(query, sortPredicate, SortOrder.Ascending);
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}
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public static IOrderedQueryable<TEntity> SortByDescending<TEntity>(this IQueryable<TEntity> query, Expression<Func<TEntity, dynamic>> sortPredicate)
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where TEntity : class, new()
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{
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return InvokeSortBy(query, sortPredicate, SortOrder.Descending);
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}
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private static IOrderedQueryable<TEntity> InvokeSortBy<TEntity>(IQueryable<TEntity> query,
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Expression<Func<TEntity, dynamic>> sortPredicate, SortOrder sortOrder)
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where TEntity : class, new()
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{
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var param = sortPredicate.Parameters[0];
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string propertyName = null;
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Type propertyType = null;
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Expression bodyExpression = null;
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if (sortPredicate.Body is UnaryExpression)
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{
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var unaryExpression = sortPredicate.Body as UnaryExpression;
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bodyExpression = unaryExpression.Operand;
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}
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else if (sortPredicate.Body is MemberExpression)
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{
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bodyExpression = sortPredicate.Body;
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}
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else
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throw new ArgumentException(@"The body of the sort predicate expression should be
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either UnaryExpression or MemberExpression.", "sortPredicate");
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var memberExpression = (MemberExpression)bodyExpression;
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propertyName = memberExpression.Member.Name;
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if (memberExpression.Member.MemberType == MemberTypes.Property)
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{
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var propertyInfo = memberExpression.Member as PropertyInfo;
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if (propertyInfo != null) propertyType = propertyInfo.PropertyType;
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}
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else
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throw new InvalidOperationException(@"Cannot evaluate the type of property since the member expression
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represented by the sort predicate expression does not contain a PropertyInfo object.");
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var funcType = typeof(Func<,>).MakeGenericType(typeof(TEntity), propertyType);
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var convertedExpression = Expression.Lambda(funcType,
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Expression.Convert(Expression.Property(param, propertyName), propertyType), param);
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var sortingMethods = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static);
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var sortingMethodName = GetSortingMethodName(sortOrder);
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var sortingMethod = sortingMethods.First(sm => sm.Name == sortingMethodName &&
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sm.GetParameters().Length == 2);
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return (IOrderedQueryable<TEntity>)sortingMethod
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.MakeGenericMethod(typeof(TEntity), propertyType)
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.Invoke(null, new object[] { query, convertedExpression });
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}
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private static string GetSortingMethodName(SortOrder sortOrder)
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{
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switch (sortOrder)
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{
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case SortOrder.Ascending:
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return "OrderBy";
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case SortOrder.Descending:
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return "OrderByDescending";
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default:
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throw new ArgumentException("Sort Order must be specified as either Ascending or Descending.",
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"sortOrder");
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}
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}
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}
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}
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