如何在 ASP.net Web 应用程序中定义全局变量

Question

I have face a requirement,

I want client access a data center but without use database , so I want my web app can retain a global or Application session variable, that contains the data, every client can access the same data... I am try to declare in golabl, but seem it only can store String but others ...

how to solve this problem ?

thanks.

Answer 1

Another option of defining a global variable is by creating a static class with a static property:

public static class GlobalVariables
{
    public static string MyGlobalVariable { get; set; }
}

You can make this more complex if you are going to use this as a data store, but the same idea goes. Say, you have a dictionary to store your global data, you could do something like this:

public static class GlobalData
{
    private static readonly object _syncRoot = new object();
    private static Dictionary<string, int> _data;

    public static int GetItemsByTag(string tag)
    {
        lock (_syncRoot)
        {
            if (_data == null)
                _data = LoadItemsByTag();

            return _data[tag];
        }
    }

    private static Dictionary<string, int> LoadItemsByTag()
    {
        var result = new Dictionary<string, int>();

        // Load the data from e.g. an XML file into the result object.

        return result;
    }
}

Answer 2

To Share the data with all application users, you can use ASP.NET Application object. Given is the sample code to access Application object in ASP.NET:

Hashtable htblGlobalValues = null;

if (Application["GlobalValueKey"] != null)
{
    htblGlobalValues = Application["GlobalValueKey"] as Hashtable;
}
else
{
    htblGlobalValues = new Hashtable();
}

htblGlobalValues.Add("Key1", "Value1");
htblGlobalValues.Add("Key2", "Value2");

this.Application["GlobalValueKey"] = htblGlobalValues;

Application["GlobalValueKey"] can be used anywhere in the whole application by any user. It will be common to all application users.

Answer 3

You can stuff data into the Application object if you want. It isn't persistent across application instances, but that may sufficient.

(I'm not for a minute going to suggest this is a best practice, but without a clearer picture of the requirements, that's all I can suggest.)

http://msdn.microsoft.com/en-us/library/system.web.ui.page.application.aspx
http://msdn.microsoft.com/en-us/library/system.web.httpapplication.aspx

Answer 4

If you are using WebApplication or MVC just go to Global.asax (in WebSite project you need to add Global.asax from the add new item menu).
I will explain to deploy two global variables for your web application:
Open the Global.asax file, then define your variable in Application_Start function as following:

void Application_Start(object sender, EventArgs e)
{
   Application.Lock();
   Application["variable1"] = "Some Value for variable1";
   Application["variable2"] = "Some Value for variable2";
   Application.UnLock();
}

If you want to use that those global variables in aspx pages just need to call them like this:

<p>I want to call variable1 <%=Application["variable1"].ToString() %></p>
<p>I want to call variable1 <%=Application["variable2"].ToString() %></p>

But if you want to use that those global variables in server-side call'em like this:

protected void Page_Load(object sender, EventArgs e)
{
   string str1 = Application["variable1"].ToString();
   string str2 = Application["variable2"].ToString();
}

Note: You must be aware that these global variables are public to all users and aren't suitable for authentication jobs.

Answer 5

您还可以使用Cache ，它具有设置过期时间/日期等优点。