有人可以帮忙吗？预先感谢 [英] Can anyone help? Thank in advance

问题描述

在运行时会出现如下异常：

while running it gives exception like below:

LINQ to Entities does not recognize the method 'Int32 Parse(System.String)' method, and this method cannot be translated into a store expression.

我尝试过：

What I have tried:

demo db = (from c in ob.demoes
                       where c.id ==Convert.ToInt32(txtboxId)
                       select c).FirstOrDefault();
            db.name = txtboxName.Text;
            db.salary = int.Parse(txtboxSalary.Text);
            ob.SaveChanges();

推荐答案

首先尝试进行转换：

Try doing the conversion first:

int id = Convert.ToInt32(txtboxId);
demo db = (from c in ob.demoes
           where c.id == id
           select c).FirstOrDefault();
db.name = txtboxName.Text;
db.salary = int.Parse(txtboxSalary.Text);
ob.SaveChanges();

但它应该是不必要的。当然，它在普通Linq中工作正常：

But it should be unnecessary. Certainly, it works fine in normal Linq:

int id = 66;
string sid = "66";
List<MyClass> list = new List<MyClass>();
MyClass mc = new MyClass();
mc.id = 55;
list.Add(mc);
mc = new MyClass();
mc.id = 66;
list.Add(mc);
var x = (from c in list
        where c.id == id
        select c).FirstOrDefault();
var y = (from c in list
         where c.id == Convert.ToInt32(sid)
         select c).FirstOrDefault();

编译并运行正常，x和y都包含相同的实例。

Compiles and runs fine, and x and y both contain the same instance.

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