How to use a getter with a nullable?

Question

I am reading a bunch of queries from a database. I had an issue with the queries not closing, so I added a CommandTimeout. Now, the individual queries read from the config file each time they are run. How would I make the code cache the int from the config file only once using a static nullable and getter. I was thinking of doing something along the lines of:

static int? var;
get{ var = null;
    if (var.HasValue)
    ...(i dont know how to complete the rest)

My actual code:

private object QueryMethod(string item)
{
    using (SqlConnection connection = new SqlConnection(item))
    {
        connection.Open();

        using (SqlCommand sql = new SqlCommand())
        {
            AddSQLParms(sql);
            sql.CommandTimeout = 30;
            sql.CommandText = _cmdText;
            sql.Connection = connection;
            sql.CommandType = System.Data.CommandType.Text;

            sql.ExecuteNonQuery();
        }
        connection.Close();
    }
    return false;
}

Answer 1

var is a system keyword - don't use it

V1 - in this version you expect config to have a value, otherwise error will occur

static int? _timeout = null;

private static int GetTimeout()
{
    if (_timeout != null) return (int)_timeout;
    _timeout = GetTimeoutFromConfig();
    return (int)_timeout;
}

V2 - in this version you will use default value if config is empty

static int? _timeout = null;
private const int def_timeout = 120;   

private static int GetTimeout()
{
    if (_timeout != null) return (int)_timeout;
    int? to = GetTimeoutFromConfig();
    _timeout = (to ?? def_timeout); 

    return (int)_timeout;
}

converting from config

private int? GetTimeoutFromConfig()
{
    int val;
    bool converted = int.TryParse(ConfigurationManager.AppSettings["TimeoutValue"], out val);

    return (converted ? val : null);
} 

Answer 2

First: don't call it var !

Let's call it cached_value.

static int? cached_value;

get { return cached_value ?? cached_value = your_logic_here }

This way, the first time you call it, if it's null, it'll initialize the field. Next time you call the getter, you'll just get the value you need.

Answer 3

You could try something like this utilizing the Lazy<T> class:

public static class ConfigCache
{
    private static Lazy<int> connectionTimeout =
        new Lazy<int>(() => int.Parse(
            ConfigurationManager.AppSettings["connectionTimeout"]));

    public static int ConnectionTimeout
    {
        get { return connectionTimeout.Value; }
    }
}

Usage:

sqlCmd.CommandTimeout = ConfigCache.ConnectionTimeout;

Answer 4

It sounds to be like you're asking how to use a Nullable variable.

static int? val;
get{ 
    if (var.HasValue)
    {
      return val.Value;
    }
    else {
       val = GetValFromConfig();
       return val.Value;
    }
} 

var is a keyword in C#