Entity Framework底層操作封裝V2版本號(3)
阿新 • • 發佈:2018-12-06
如今是附加的。組合查詢須要的擴充套件類。
大家知道lanmda表示式的組合條件比較麻煩。所以就加了一樣一個類,方便進行組合查詢:
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Linq.Expressions; namespace JFrame.AccessCommon { public static class PredicateExtensions { public static Expression<Func<T, bool>> True<T>() { return f => true; } public static Expression<Func<T, bool>> False<T>() { return f => false; } public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expression1, Expression<Func<T, bool>> expression2) { var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast<Expression>()); return Expression.Lambda<Func<T, bool>>(Expression.Or(expression1.Body, invokedExpression), expression1.Parameters); } public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expression1, Expression<Func<T, bool>> expression2) { var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast<Expression>()); return Expression.Lambda<Func<T, bool>>(Expression.And(expression1.Body, invokedExpression), expression1.Parameters); } } }