当将方法转换为字符串时，LinQ无法理解

问题描述

您能教我更多有关此linq代码如何工作的信息吗? string pass = HashPassword(password)是一个字符串，HashPassword(password)也返回一个字符串.

Can you teach me more about how does this linq code work? string pass = HashPassword(password) is a string, HashPassword(password) returns a string too.

但是LinQ在比较之前需要一个变量来存储字符串.像这样:

But the LinQ needs a variable to store the string before comparing. Like this:

public bool Login(string email, string password)
        {
            try
            {
                string pass = HashPassword(password);
                var acc = db.UserAccount.SingleOrDefault(x => x.Email == email && x.HashPassword == pass);
                if (acc != null)
                {
                    return true;
                }
                // email or password is not matched
                return false;
            }
            catch { return false; }
        }

和散列密码的方法:

private string HashPassword(string password)
{
    return BitConverter.ToString(new SHA256CryptoServiceProvider().ComputeHash(Encoding.UTF8.GetBytes(password))).Replace("-", "");
}

自从我更改了行var acc = db.UserAccount.SingleOrDefault(x => x.Email == email && x.HashPassword == pass);

到

var acc = db.UserAccount.SingleOrDefault(x => x.Email == email && x.HashPassword == HashPassword(password));

那是行不通的.为什么?

It wouldn't work. Why?

推荐答案

您的声明:var acc = db.UserAccount.SingleOrDefault(x => x.Email == email && x.HashPassword == HashPassword(password));导致异常并跳转到catch语句.以下是原因.

Your statement: var acc = db.UserAccount.SingleOrDefault(x => x.Email == email && x.HashPassword == HashPassword(password)); is causing an exception and jumping to the catch-statement. Below is the reason why.

有效地，LINQ不知道如何处理您的函数，而它仅与x.HashPassword == pass一起工作的原因是因为这只是一个简单的字符串比较.

Effectively LINQ doesn't know how to handle your function and the reason why it works with just x.HashPassword == pass is because that's just a simple string comparison.

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