How can I call an Interface's property in the same interface's method while implementing the interface in C#

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C#

Hi All,
m wondering how I can call an Interface's Property (that is defined in a class that implements that interface) in the same Interface's method (in the same class of the previous Interface's property)
Here is the code:

namespace interfacetest
{
  public interface IocExt
  {
    void LoadProperties();
    void UpdateProperties();
    string Properties
    { get; }
  }
  public class ocExt : IocExt
  {
    public string colNameGUID;
    void IocExt.LoadProperties()
    {
       colNameGUID = "GUID";
       Messagebox.Show("LoadProperties()- colNameGUID = " + colNameGUID);
    }
    string IocExt.Proeprties
    {
       get{ return colNameGUID; }
    }
    void IocExt.UpdateProperties()
    {
      IocExt ext = new ocExt();
      string s = "UpdateProperties()- colNameGUID = " +   ext.Properties; // here is the problem: 'colNameGUID' value
                                           could not be retrieved from LoadProeprties that is = "GUID" and it just has " "
      Messagebox.Show(s);
    }
  }
  public partial class ocExtImplement : Form
  {
    private void button3_click(object sender, EventArgs e)
    {
      IocExt ioc = new ocExt();
      ioc.LoadProperties();
      ioc.UpdateProperties();
    }
  }
}

Output:
LoadProperties()- colNameGUID = GUID
UpdateProperties() - colNameGUID = .
I'm expecting the second line should also display UpdateProperties() - colNameGUID = GUID. (instead of blank value)
Any ideas of how I can call string IocExt.Proeprties at IocExt.UpdateProperties()?
Thanks in advance!

[edit]Code block added to preserve formatting - OriginalGriff[/edit]