c# – 为什么布尔变量总是重置为false;

我在类的顶部声明了一个布尔变量,当在页面上选择单选按钮时,变量设置为true,但是当重新加载页面时,变量将重置为false.我处理此问题的一种方法是使用static关键字,但我不确定这是否是处理此问题的最佳方法.这是我尝试在Page_Load事件中执行操作的类,但它仍然将变量重置为false.

public class SendEmail
{
    bool AllSelected;

protected void Page_Load(object sender,EventArgs e)
{
    if(!Page.IsPostBack)
    {
        AllSelected = false;
    }
}

protected void rbAll_SelectedIndexChanged(object sender,EventArgs e)
{
    if(rbAll.SelectedValue == "All")
       AllSelected = true;
}

public Send()
{
   if(AllSelected)
   {
       //Send Email. Never runs because AllSelected is always false;
   }
}

}

bool AllSelected
{
    get
    {
        object o = ViewState["AllSelected"];
        if(o == null) return false;
        return (bool)o;
    }
    set
    {
        ViewState["AllSelected"] = value;
    }
}