Why can't empty value be realized?

[enrc66]

string ua=project.Variables["ua"].Value;
if(ua.IndexOf("MSIE")>-1)//ie
{
	project.Variables["cpuclass"].Value="x86";
}
else
{
	project.Variables["cpuclass"].Value=null;
}
instance.SetHeader("http_user_agent_cpuclass", project.Variables["cpuclass"].Value);

I want to realize that if the browse is ie ,then the value of "cpuclass" is "x86", else
the value of "cpuclass" is empty
how to realize that ?

find the result from open
http://www.w3school.com.cn/tiy/t.asp?f=hdom_navigator

 

[enrc66]

string ua=project.Variables["ua"].Value;
if(ua.IndexOf("MSIE")>-1)//ie
{
    project.Variables["cpuclass"].Value="x86";
}
else
{
    project.Variables["cpuclass"].Value="test";
}
instance.SetHeader("http_user_agent_cpuclass", project.Variables["cpuclass"].Value);

if the browse is ie then cpuclass is "x86" ,

else cpuclass is "test"

can realize ,why?

 

[rostonix]

You cant use null or blank values for headers.
We will add option to disable headers in future builds.

 

[enrc66]

I see.thanks,