Question

我有一个字典，我放在会话中，每按一次按钮，我需要执行一些操作。

itemColl = new Dictionary<int, int>();

我想搜索我在会话变量中维护的密钥，如果密钥存在，那么我想将相应密钥的值增加1，我该怎样才能实现。

我正在尝试如下：

if (Session["CurrCatId"] != null)
{
    CurrCatId = (int)(Session["CurrCatId"]);
    // this is the first time, next time i will fetch from session
    // and want to search the currcatid and increase the value from
    // corresponding key by 1.
    itemColl = new Dictionary<int, int>();
    itemColl.Add(CurrCatId, 1);
    Session["itemColl"] = itemColl;                            
}

Answer 1

你非常接近，你只需要管理一些案例：

if (Session["CurrCatId"] != null)
{
    CurrCatId = (int)(Session["CurrCatId"]);

    // if the dictionary isn't even in Session yet then add it
    if (Session["itemColl"] == null)
    {
        Session["itemColl"] = new Dictionary<int, int>();
    }

    // now we can safely pull it out every time
    itemColl = (Dictionary<int, int>)Session["itemColl"];

    // if the CurrCatId doesn't have a key yet, let's add it
    // but with an initial value of zero
    if (!itemColl.ContainsKey(CurrCatId))
    {
        itemColl.Add(CurrCatId, 0);
    }

    // now we can safely increment it
    itemColl[CurrCatId]++;
}

Answer 2

编辑：抱歉，我之前没有理解这个问题。您只需尝试使用该密钥，如下所示：

try
{
    if (condition)
        itemColl[i]++;
}
catch
{
    // ..snip
}

使用try-catch，如果由于某种原因钥匙不在那里，您就可以处理错误。

Answer 3

var itemColl = Session["itemColl"];
if (!itemColl.ContainsKey(CurrCatId))
    itemColl[CurrCatId] = 0;
itemColl[CurrCatId]++;

循环遍历字典集合以搜索键并增加值

3 个答案: