using System; using System.Collections.Generic; using System.Linq; using System.Linq.Expressions; using System.Reflection; using System.Text; namespace foda { public static class LambdaHelper { /// <summary> /// 创建lambda表达式:p=>true /// </summary> /// <typeparam name="T"></typeparam> /// <returns></returns> public static Expression<Func<T, bool>> True<T>() { return p => true; } /// <summary> /// 创建lambda表达式:p=>false /// </summary> /// <typeparam name="T"></typeparam> /// <returns></returns> public static Expression<Func<T, bool>> False<T>() { return p => false; } /// <summary> /// 创建lambda表达式:p=>p.propertyName /// </summary> /// <typeparam name="T"></typeparam> /// <typeparam name="TKey"></typeparam> /// <param name="sort"></param> /// <returns></returns> public static Expression<Func<T, TKey>> GetOrderExpression<T, TKey>(string propertyName) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p"); return Expression.Lambda<Func<T, TKey>>(Expression.Property(parameter, propertyName), parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName == propertyValue /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> CreateEqual<T>(string propertyName, object propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); ConstantExpression constant = Expression.Constant(propertyValue);//创建常数 return Expression.Lambda<Func<T, bool>>(Expression.Equal(member, constant), parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName != propertyValue /// </summary> /// <typeparam name="T"></typeparam> /// <param name="propertyName"></param> /// <param name="propertyValue"></param> /// <returns></returns> public static Expression<Func<T, bool>> CreateNotEqual<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); ConstantExpression constant = Expression.Constant(propertyValue);//创建常数 return Expression.Lambda<Func<T, bool>>(Expression.NotEqual(member, constant), parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName > propertyValue /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> CreateGreaterThan<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); ConstantExpression constant = Expression.Constant(propertyValue);//创建常数 return Expression.Lambda<Func<T, bool>>(Expression.GreaterThan(member, constant), parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName < propertyValue /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> CreateLessThan<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); ConstantExpression constant = Expression.Constant(propertyValue);//创建常数 return Expression.Lambda<Func<T, bool>>(Expression.LessThan(member, constant), parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName >= propertyValue /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> CreateGreaterThanOrEqual<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); ConstantExpression constant = Expression.Constant(propertyValue);//创建常数 return Expression.Lambda<Func<T, bool>>(Expression.GreaterThanOrEqual(member, constant), parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName <= propertyValue /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> CreateLessThanOrEqual<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); ConstantExpression constant = Expression.Constant(propertyValue);//创建常数 return Expression.Lambda<Func<T, bool>>(Expression.LessThanOrEqual(member, constant), parameter); } //时间比较>= public static Expression<Func<T, bool>> CreateCompareToLater<T>(string propertyName, object propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); var methodInfo = typeof(DateTime).GetMethod("CompareTo", new Type[] { typeof(DateTime) });// ConstantExpression constant = Expression.Constant(Convert.ToDateTime(propertyValue), typeof(DateTime));//创建常数 BinaryExpression siteNoExpression = Expression.GreaterThanOrEqual( Expression.Call( member, methodInfo, constant ), Expression.Constant(0, typeof(Int32)) //比较String.CompareTo的返回结果和0,来实现>=的效果 ); return Expression.Lambda<Func<T, bool>>(siteNoExpression, parameter); } //时间比较<= public static Expression<Func<T, bool>> CreateCompareToEarlier<T>(string propertyName, object propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//创建参数p MemberExpression member = Expression.PropertyOrField(parameter, propertyName); var methodInfo = typeof(DateTime).GetMethod("CompareTo", new Type[] { typeof(DateTime) });// ConstantExpression constant = Expression.Constant(Convert.ToDateTime(propertyValue), typeof(DateTime));//创建常数 BinaryExpression siteNoExpression = Expression.LessThanOrEqual( Expression.Call( member, methodInfo, constant ), Expression.Constant(0, typeof(Int32)) //比较String.CompareTo的返回结果和0,来实现>=的效果 ); return Expression.Lambda<Func<T, bool>>(siteNoExpression, parameter); } /// <summary> /// 创建lambda表达式:p=>p.propertyName.Contains(propertyValue) /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> GetContains<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p"); MemberExpression member = Expression.PropertyOrField(parameter, propertyName); MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) }); ConstantExpression constant = Expression.Constant(propertyValue, typeof(string)); return Expression.Lambda<Func<T, bool>>(Expression.Call(member, method, constant), parameter); } /// <summary> /// 创建lambda表达式:!(p=>p.propertyName.Contains(propertyValue)) /// </summary> /// <typeparam name="T"></typeparam> /// <param name="column"></param> /// <param name="value"></param> /// <returns></returns> public static Expression<Func<T, bool>> GetNotContains<T>(string propertyName, string propertyValue) { ParameterExpression parameter = Expression.Parameter(typeof(T), "p"); MemberExpression member = Expression.PropertyOrField(parameter, propertyName); MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) }); ConstantExpression constant = Expression.Constant(propertyValue, typeof(string)); return Expression.Lambda<Func<T, bool>>(Expression.Not(Expression.Call(member, method, constant)), parameter); } public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) { var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); return Expression.Lambda<Func<T, bool>> (Expression.Or(expr1.Body, invokedExpr), expr1.Parameters); } public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) { var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); return Expression.Lambda<Func<T, bool>> (Expression.And(expr1.Body, invokedExpr), expr1.Parameters); } } }