拼接LINQ动态表达式

时间:2023-03-09 20:05:03
拼接LINQ动态表达式
using System;
using System.Linq;
using System.Linq.Expressions; public static class LinqBuilder
{
/// <summary>
/// 默认True条件
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static Expression<Func<T, bool>> True<T>() { return f => true; } /// <summary>
/// 默认False条件
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static Expression<Func<T, bool>> False<T>() { return f => false; } /// <summary>
/// 拼接 OR 条件
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="exp"></param>
/// <param name="condition"></param>
/// <returns></returns>
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> exp, Expression<Func<T, bool>> condition)
{
var inv = Expression.Invoke(condition, exp.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>(Expression.Or(exp.Body, inv), exp.Parameters);
} /// <summary>
/// 拼接And条件
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="exp"></param>
/// <param name="condition"></param>
/// <returns></returns>
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> exp, Expression<Func<T, bool>> condition)
{
var inv = Expression.Invoke(condition, exp.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>(Expression.And(exp.Body, inv), exp.Parameters);
}
} public class Entity
{
public int Id { get; set; }
public string Name { get; set; }
} public class Example
{
public Example()
{
var linq = LinqBuilder.True<Entity>();
linq.And(p => p.Id == );
Expression<Func<Entity, bool>> condition = linq.Or(p => p.Name == "");
}
}