LoadViewState中的對象引用null？

Question

當我檢查，如果按鈕被點擊或不LoadViewState

我得到這個錯誤

Object reference null 

在下面的代碼，如果我點擊Add經驗按鈕時 eTarget = Request.Params["btnAddVisa"].ToString();得到零誤差

代碼：

protected override void LoadViewState(object savedState) 
{ 
    base.LoadViewState(savedState); 
    if(IsPostBack) 
    { 

    eTarget = Request.Params["btnAddVisa"].ToString(); 
    eTarget = Request.Params["btnAddExperience"].ToString(); 
    } 

    if(eTarget == "Add Visa") 
    { 
    // 
    } 

    if(eTarget == "Add Experience") 
    { 
    // 
    } 
} 

protected void btnAddVisa_Click(sender,e) 
{ 
    // 
} 

protected void btnAddExperience_Click(sender,e) 
{ 
    // 
} 

任何想法？在此先感謝

Answer 1

你需要檢查空值

if(Request.Params["btnAddVisa"]!=null) 
    eTarget = Request.Params["btnAddVisa"].ToString(); 
if(Request.Params["btnAddExperience"]!=null) 
    eTarget = Request.Params["btnAddExperience"].ToString(); 

Answer 2

Request.Params["btnAddVisa"] may not have any object or value.