如何将null coockie值存储到字符串变量中？ [英] How to store null coockie value into string variable?

问题描述

我想尝试在下面但是抛出错误

I am trying to like below but throwing an error "

Object reference not set to an instance of an object.

"

string roll = Request.Cookies["StudentCookies"].Value;
            if (roll == null || roll == String.Empty)
            {
                Response.Redirect("~/LoginPage.aspx");
            }

推荐答案

尝试：

Try:

string roll = Request.Cookies["StudentCookies"] == null ? "" : Request.Cookies["StudentCookies"].Value;

您正在尝试使用Request.Cookies.Value而不检查它存在cookie。



这是正确的检查：

You are trying to use Request.Cookies.Value without checking it the cookie exists.

This is the correct check:

string roll = string.Empty;
// first check that cookie exists, if it does, use the value
if (Request.Cookies["StudentCookies"] != null) {
    roll = Request.Cookies["StudentCookies"].Value;
}

' if cookie wasn't present or the value is empty, redirect
if ( roll == string.empty)
    Response.Redirect("~/LoginPage.aspx");


Good luck.

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