从其他文件向数据表添加行

Question

I have created a data table of four columns in my global.asax file. I am adding rows only to two columns of the data table in the global.asax file. I am trying to add the other two rows from a different .aspx.cs file which is under the same project. When I try to add the row, it gives me an error

"the name "dr" does not exists in the current context".

My code:

login.aspx.cs:

protected void btnLogin_Click(object sender, EventArgs e)
{
    if(txtPassword.Text == "")
    {            
        Server.Transfer("Main.aspx", true);            
    }

    if(txtUserName.Text!= "" && txtPassword.Text!= "")
    {
        Server.Transfer("Userlog.aspx", true);
    }


    dr["username"] = Session["UserName"]; // username
    dr["login_time"] = Session["LoginTime"]; //login time
}

global.asax:

void Session_Start(Object s, EventArgs e)
{

    Application.Lock();

    dt = new DataTable();
    dt.Columns.Add(new DataColumn("session_id", System.Type.GetType("System.String")));
    dt.Columns.Add(new DataColumn("username",   System.Type.GetType("System.String")));
    dt.Columns.Add(new DataColumn("login_time", System.Type.GetType("System.DateTime")));
    dt.Columns.Add(new DataColumn("ip_address", System.Type.GetType("System.String")));

    Application["visitorTable"] = dt;

    DataRow dr = dt.NewRow();

    dr["session_id"] = (System.String)Session.SessionID; // session id
    dr["ip_address"] = Request.ServerVariables["SERVER_NAME"]; //ip-address

    dt.Rows.Add(dr);

    //dt = (DataTable)Application["visitorTable"];

    Application["visitorTable"] = dt;

    DataView view = new DataView(dt);
    Application.UnLock();

}

Answer 1

It will through since dr variable doesnt exists. If you want the datatable row in session object then store the datatable row with some key word and then retrieve it.

Session["RowDataTable"] = dr;

Then login page

var dr = Session["RowDataTable"] as DataRow;

Answer 2

Hmm don't realy know where to start:

Firstly your defined variables dt and dr are only available in the scope of the method Session_Start(){}. That means, after the method-call, the both variables are not available anymore.

Secondary, if you need to access your Data also outside of that method, you should store it in an private variable:

private DataTable _myDataTable;

or in a public Propertiy to access it from outside the current class:

public DataTable MyDataTable { get; set }

You should also inform you about the static modifier:

https://msdn.microsoft.com/de-de/library/98f28cdx.aspx

Hope that helps you a little bit.

And for that what you want in the current situation, the answer of Mahesh Malpani maybe leads you to.