合并目录树表达式 And Or Not扩展

using ExpressionDemo.Visitor;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;

namespace ExpressionDemo.Extend
{
/// <summary>
/// 合并表达式 And Or Not扩展
/// </summary>
public static class ExpressionExtend
{
/// <summary>
/// 合并表达式 expr1 AND expr2
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expr1"></param>
/// <param name="expr2"></param>
/// <returns></returns>
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
{
//return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body, expr2.Body), expr1.Parameters);
if (expr1 == null)
return expr2;
else if (expr2 == null)
return expr1;
ParameterExpression newParameter = Expression.Parameter(typeof(T), "c");
NewExpressionVisitor visitor = new NewExpressionVisitor(newParameter);
var left = visitor.Replace(expr1.Body);
var right = visitor.Replace(expr2.Body);
var body = Expression.And(left, right);
return Expression.Lambda<Func<T, bool>>(body, newParameter);
}
/// <summary>
/// 合并表达式 expr1 or expr2
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expr1"></param>
/// <param name="expr2"></param>
/// <returns></returns>
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
{
if (expr1 == null)
return expr2;
else if (expr2 == null)
return expr1;
ParameterExpression newParameter = Expression.Parameter(typeof(T), "c");
NewExpressionVisitor visitor = new NewExpressionVisitor(newParameter);

var left = visitor.Replace(expr1.Body);
var right = visitor.Replace(expr2.Body);
var body = Expression.Or(left, right);
return Expression.Lambda<Func<T, bool>>(body, newParameter);
}
public static Expression<Func<T, bool>> Not<T>(this Expression<Func<T, bool>> expr)
{
if (expr == null) return null;
var candidateExpr = expr.Parameters[0];
var body = Expression.Not(expr.Body);

return Expression.Lambda<Func<T, bool>>(body, candidateExpr);
}
}
}