Linq to sql 动态查询
辅助类
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Linq.Expressions; 5 using System.Text; 6 using System.Threading.Tasks; 7 8 namespace Drision.Framework.Logic.NYZF 9 { 10 public static class PredicateBuilder 11 { 12 public static Expression<Func<T, bool>> True<T>() { return f => true; } 13 public static Expression<Func<T, bool>> False<T>() { return f => false; } 14 15 public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, 16 Expression<Func<T, bool>> expr2) 17 { 18 var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); 19 return Expression.Lambda<Func<T, bool>> 20 (Expression.Or(expr1.Body, invokedExpr), expr1.Parameters); 21 } 22 23 public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, 24 Expression<Func<T, bool>> expr2) 25 { 26 var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); 27 return Expression.Lambda<Func<T, bool>> 28 (Expression.And(expr1.Body, invokedExpr), expr1.Parameters); 29 } 30 } 31 }
使用方法
1 var predicate = PredicateBuilder.False<T_Operator>(); 2 foreach (var name in typenames) 3 { 4 string tmpname = name; 5 predicate = predicate.Or(o => o.OperatingRange != null && o.OperatingRange.Contains(tmpname)); 6 } 7 operators = operators.AsQueryable().Where(predicate).ToList();
