Question

I would like to have a dictionary object contains string keys and values, which are generated from the database. But, I only need to run once when page loads. (C# .NET)

In which way can I do that? I tried the following:

public static class GlobalVar
{
    static Dictionary<string, string> GenerateLoginStatus(Dictionary<string, string> List)
    {
        string Query = "SELECT * FROM LoginStatus";
        DataTable Types = MyAdoHelper.ExecuteDataTable(GlobalVar.dbName, Query);
        foreach (DataRow Row in Types.Rows)
        {
            List.Add(Row["Status_Title"].ToString(), Row["Status_Info"].ToString());
        }
        return List;
    }

    public const string GlobalString = "ProjectDatabase.mdf";

    public static Dictionary<string, string> LoginTypes = GenerateLoginStatus(LoginTypes);

}

Table structure:

Status_Title        Status_Info

AlreadyLoggedIn     User is already logged in.

A                   B

C                   D

And I use it in another page: GlobalVar.LoginStatus["AlreadyLoggedIn"]

The “AlreadyLoggedIn” is created in the database for sure, but when I call any of the keys, it returns an exception (doesn’t tell which exception).

EDIT: I changed the code a bit, and it now gives “The type initializer for ‘GlobalVar’ threw an exception.”

Answer 1

I suppose you might be getting null reference exception which is caused because you call your static initialization method with instance you want to initialize (LoginTypes):

public static Dictionary<string, string> LoginTypes =
    GenerateLoginStatus(LoginTypes);

When GenerateLoginStatus executes, LoginTypes is null. Yet you attempt to add items to it:

static Dictionary<string, string> GenerateLoginStatus(
    Dictionary<string, string> List)
{
    // ...
    List.Add(Row["Status_Title"].ToString(), Row["Status_Info"].ToString());

This causes null reference exception. You should use type constructor and create that dictionary there:

static GlobalVar()
{
    LoginTypes = new Dictionary<string, string>();
    // proceed with initialization
}