private static readonly SingletonClass instance = new SingletonClass();
public static SingletonClass Instance
{
   get
   {
        return instance;
   }
}

private static SingletonClass instance;
public static GetInstance
{
    get
    {
       if(instance == null)
       {
         instance = new SingletonClass();
       }
       return instance;
    }
}

public class MyClass
{
    private DataTable _dt;
    public DataTable GetDt
    {
        get
        {
            if (_dt == null)
            {
                _dt = new DataTable();
                _dt.Columns.Add("Column1", typeof(string));
                _dt.Columns.Add("Column2", typeof(string));
                _dt.Rows.Add(new string[] { "cell1", "cell2" });
            }
            return _dt;
        }
    }
}