C# 值不能为空。参数名称：字符串
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Value cannot be null. Parameter name: String
提问by Kush
Please take a look at the following code. It's in handler.asxh.
请看下面的代码。它在handler.asxh.
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "application/json";
new RequestManagementFacade().PinRequest(Int32.Parse(context.Request.QueryString["requestId"]), (Boolean.Parse(context.Request.QueryString["isPinned"])));
}
This is showing the following error:
这显示以下错误：
Value cannot be null. Parameter name: String
There is value being passed as I have checked the context request query string, however, the code breaks at this stage.
由于我检查了上下文请求查询字符串，因此传递了值，但是，代码在此阶段中断。
This handler will connect to the business logic layer.
此处理程序将连接到业务逻辑层。
采纳答案by Jon Skeet
There is value being passed as i have checke dthe context request query string
由于我检查了上下文请求查询字符串，因此传递了值
I strongly suspect your diagnostics are incorrect then. Values don't magically go missing - you need to question your assumptions. This is easy to debug through though. I would suggest changing your code to:
我强烈怀疑您的诊断不正确。价值观不会神奇地消失——你需要质疑你的假设。不过，这很容易调试。我建议将您的代码更改为：
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "application/json";
string requestId = context.Request.QueryString["requestId"];
string isPinned = context.Request.QueryString["isPinned"];
var facade = new RequestManagementFacade();
facade.PinRequest(Int32.Parse(requestId), Boolean.Parse(isPinned));
}
It's then reallysimple to step through and find out what's going on.
然后就可以很容易地逐步完成并找出发生了什么。
回答by Levi Botelho
It is likely that either context.Request.QueryString["requestId"]or context.Request.QueryString["isPinned"]is not returning a valid string value. Check that both values are passed in the query string with the proper IDs, those being of course requestIdand isPinned.
很可能要么context.Request.QueryString["requestId"]或未context.Request.QueryString["isPinned"]返回有效的字符串值。检查两个值是否都通过正确的 ID 在查询字符串中传递，这些当然是requestId和isPinned。
回答by Kush
Okay solved when passing the values to the handler i inserted it as
好的，当将值传递给处理程序时解决了，我将其插入为
"PinRequest.ashx?="+requestId+isPinned"
Which gave me the result 2True
这给了我结果 2True
So i realised the hiccup was with not including the string names
所以我意识到打嗝是不包括字符串名称
"PinRequest.ashx?requestId=" + this._requestId + "&isPinned=" + this._isPinned
Thanks for you help guys
谢谢你们的帮助
LeviBotelho Thank you made me check something i was missing out when checking as its javascript
LeviBotelho 谢谢你让我检查一些我在检查 javascript 时遗漏的东西
