Expression<Func<Student, bool>> express1 = s => s.Name.Contains("奥特曼");
            Expression<Func<Student, bool>> express2 = s => s.Age>600000;

            //声明传递参数（也就是上面表达式树里面的参数s）
            ParameterExpression s = Expression.Parameter(typeof(Student), "s");
            //统一管理参数，保证参数一致，否则会报错 变量未定义
            MyExpressionVisitor visitor = new MyExpressionVisitor(s);
            //表达式树内容
            Expression body1 = visitor.Visit(express1.Body);
            Expression body2 = visitor.Visit(express2.Body);
            //合并表达式
            Expression<Func<Student, bool>> finalEx = Expression.Lambda<Func<Student, bool>>(Expression.AndAlso(body1, body2), s);

            //调用
            List<Student> list = stuList.Where(finalEx.Compile()).ToList();

public class MyExpressionVisitor : ExpressionVisitor
    {
        public ParameterExpression _Parameter { get; set; }

        public MyExpressionVisitor(ParameterExpression Parameter)
        {
            _Parameter = Parameter;
        }
        protected override Expression VisitParameter(ParameterExpression p)
        {
            return _Parameter;
        }

        public override Expression Visit(Expression node)
        {
            return base.Visit(node);//Visit会根据VisitParameter()方法返回的Expression修改这里的node变量
        }
    }