58 lines
2.5 KiB
C#
58 lines
2.5 KiB
C#
using System;
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using System.Collections.Generic;
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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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using System.Text;
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using System.Threading.Tasks;
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using System.Diagnostics.Contracts;
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namespace APT.Infrastructure.Core
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{
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public static class QueryableOrderExtension
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{
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public static IQueryable<T> SetQueryableOrder<T>(this IQueryable<T> query, string sort, string order, bool isThen = false)
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{
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if (string.IsNullOrEmpty(sort))
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throw new Exception("必须指定排序字段!");
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//PropertyInfo sortProperty = typeof(T).GetProperty(sort, BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase);
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//if (sortProperty == null)
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// throw new Exception("查询对象中不存在排序字段" + sort + "！");
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ParameterExpression param = Expression.Parameter(typeof(T), "t");
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Expression body = param;
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if (Nullable.GetUnderlyingType(body.Type) != null)
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body = Expression.Property(body, "Value");
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body = GetPropertyLambdaExpression(body, sort);
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LambdaExpression keySelectorLambda = Expression.Lambda(body, param);
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if (string.IsNullOrEmpty(order))
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order = "ASC";
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string queryMethod = isThen ? order.ToUpper() == "DESC" ? "ThenByDescending" : "ThenBy" : order.ToUpper() == "DESC" ? "OrderByDescending" : "OrderBy";
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query = query.Provider.CreateQuery<T>(Expression.Call(typeof(Queryable), queryMethod,
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new Type[] { typeof(T), body.Type },
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query.Expression,
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Expression.Quote(keySelectorLambda)));
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return query;
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}
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private static Expression GetPropertyLambdaExpression(Expression body, string fileName)
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{
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string[] propertyNames = fileName.Split('.');
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Type type = body.Type;
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foreach (string propertyName in propertyNames)
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{
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PropertyInfo property = type.GetProperty(propertyName);
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//Contract.Assume(property != null);
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if (property == null)
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{
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throw new Exception($"类型{type.Name}不存在属性{propertyName}");
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}
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type = property.PropertyType;
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body = Expression.MakeMemberAccess(body, property);
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}
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return body;
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}
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}
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}
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