无法将null值分配给类型为System.Int32的成员，该类型是非可空值类型。

问题描述：

亲爱的朋友

我在开发程序时遇到问题。当我使用LINQ在数据库中插入值时，我得到的错误表明：

无法将null值分配给类型为System.Int32的成员，该类型为非可空值类型。

相同的代码如下：

Dear Friend
I have problem when developing a program.When i insert value in database using LINQ then i get the error which states that:

"The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type".

Code for the same is as follows :

db = new MCTDBDataContext();
 var company = db.Companies.Where(c => c.CompanyName == txtCompanyName.Text).SingleOrDefault();

 if (company.CompanyID.Equals(null))
   {

           MCTWeb.Model.CompanyUser cu = new MCTWeb.Model.CompanyUser();
           cu.CompanyId = company.CompanyID;
           cu.UserId = userid;
           db.CompanyUsers.InsertOnSubmit(cu);
           db.SubmitChanges();
}

数据库设计： -

CompanyUsers Table ： -

CompanyId int not null辅助密钥

UserId uniqueidentifier not null辅助密钥

我在谷歌上提到了所有程序，但没有一个解决了问题所以请尽快给我信息如何解决这个问题。

先谢谢!!

语法错误

答

如果在DB中设置为非空，则以下行不合逻辑

if（company.CompanyID.Equals（null））

i会建议以下实施

if is set a not null in DB, the following line is not logical
if (company.CompanyID.Equals(null))

i would suggest the following implementation

var company = db.Companies.Where(c => c.CompanyName == txtCompanyName.Text).SingleOrDefault();


/*The following will check if the company name exists in the DB as per the query above then do an update*/
 if (company !=null)
   {

           MCTWeb.Model.CompanyUser cu = new MCTWeb.Model.CompanyUser();
           cu.CompanyId = company.CompanyID;
           cu.UserId = userid;
           db.CompanyUsers.InsertOnSubmit(cu);
           db.SubmitChanges();
}

db = new MCTDBDataContext();
 var company = db.Companies.Where(c => c.CompanyName == txtCompanyName.Text);

 if (company.Count()==0)
   {

           MCTWeb.Model.CompanyUser cu = new MCTWeb.Model.CompanyUser();
           cu.CompanyId = company.CompanyID;
           cu.UserId = userid;
           db.CompanyUsers.InsertOnSubmit(cu);
           db.SubmitChanges();
}

是的，错误很明显。 CompanyId或UserId（或可能是两者）中的任何一个都可以在您的数据库中为空。

试试这个：

Yes, the error is obvious. Either of CompanyId or UserId(or may be both) is nullable in your database.
Try this:

if (company != null)
{
    MCTWeb.Model.CompanyUser cu = new MCTWeb.Model.CompanyUser();
    cu.CompanyId = Convert.ToInt32(company.CompanyID);
    cu.UserId = Convert.ToInt32(userid);
    db.CompanyUsers.InsertOnSubmit(cu);
    db.SubmitChanges();
}

- Amit

无法将null值分配给类型为System.Int32的成员，该类型是非可空值类型。

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