c# - 如何将 queryString 值更改为 (int)

Question

可能重复：
如何将 String 转换为 Int？

如何将 queryString 值更改为 (int)

string str_id;
str_id = Request.QueryString["id"];
int id = (int)str_id;

Answer 1

使用Int32.TryParse 方法安全地获取int值：

int id;
string str_id = Request.QueryString["id"];
if(int.TryParse(str_id,out id))
{
    //id now contains your int value
}
else
{
    //str_id contained something else, i.e. not int
}

Answer 2

换成这个

string str_id;
str_id = Request.QueryString["id"];
int id = Convert.ToInt32(str_id);

或者更简单、更有效的

string str_id;
str_id = Request.QueryString["id"];
int id = int.Parse(str_id);

Answer 3

int id = Convert.ToInt32(str_id, CultureInfo.InvariantCulture);

Answer 4

有几种方法可以做到这一点

string str_id = Request.QueryString["id"];

int id = 0;

//this prevent exception being thrown in case query string value is not a valid integer
Int32.TryParse(str_id, out id); //returns true if str_id is a valid integer and set the value of id to the value. False otherwise and id remains zero

其他

int id = Int32.Parse(str_id); //will throw exception if string is not valid integer
int id = Convert.ToInt32(str_id);  //will throw exception if string is not valid integer

Answer 5

你必须使用int.Parse(str_id)

编辑 ：不要相信用户输入

最好在解析之前检查输入是否为数字，为此使用int.TryParse