值未从javascript传递到c#

Asp.net

c#

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username1获取空值。有人可以检查它是否正确吗？

通过页面请求显式检索

string username1 = hdnfldVariable.Value;

document.getElementById（“”）可能重复的
function GetUserName() {
        var wshell = new ActiveXObject("WScript.Shell");
        var unamer = document.getElementById('hdnfldVariable');
        unamer.value = wshell.ExpandEnvironmentStrings("%USERNAME%");
    }

string username1 = hdnfldVariable.Value;

 string  username1 = Page.Request.Form["hdnfldVariable"].ToString();