将NULL转换为0的问题 [英] Problems with converting NULL to 0

问题描述

您好。



请帮我解决以下问题。我有一个DataRow r，填充了我数据库中的数据。现在我要填写一个MVC模型

Hi there.

Help me please with the following problem. I have a DataRow r, filled with data from my database. Now I want to fill an MVC model

public class Customer
{
    private int id;
    private string name;
    private string region;
    private int phone;

    public int Id {get, set}
    public string Name {get, set}
    public string Region {get, set}
    public int Phone {get, set}
}

如下所示

as shown below

var c = new Customer {
   Id = Convert.ToInt32(r[0]),
   Name = r[1].ToString(),
   Region = r[2].ToString(),
   Phone = Convert.ToInt32(r[3])
   }

问题是r [3]对应于可选数据，如果我的数据库中存在NULL，则会发生转换错误。在r [3]为NULL的情况下，我可以使用什么来使Phone变为0？

The problem is that r[3] corresponds to optional data, and if there is NULL in my database, an error with Convert occurs. What can I use to make Phone to be just 0 in the case when r[3] is NULL ?

推荐答案

将它作为值存储在类中的问题0是如果你将它保存回数据库，你可能会用0覆盖NULL值。



更好的选择是使用Nullable< int>数据类型，允许表示缺失值或电话号码。



此外，电话号码最好存储为字符串。它们比一个数字更复杂。有些有重要的前导0，有些可能是国际的，有些可能比整数可以代表的大。

The problem with storing it in your class as value of 0 is that if you save it back to the database, you will possibly overwrite the NULL value with 0.

A better option is to use the Nullable<int> data type, which allows representation of a missing value, or the phone number.

Also, phone numbers are better stored as strings. They are more complex than just a number. Some have important leading 0's, some may be international, some may be bigger than what an integer can represent.

你应该可以使用 Convert.IsDBNull

You should be able to use Convert.IsDBNull

var c = new Customer {
        Id = Convert.ToInt32(r[0]),
        Name = r[1].ToString(),
        Region = r[2].ToString(),
        Phone = Convert.IsDBNull(r[3]) ? 0 : Convert.ToInt32(r[3])
        }

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