GUI is not updated by using Two way binding in wpf

I'm working on project where I'm using MVVM pattern.

I have one text box:

<TextBox Height="23" HorizontalAlignment="Right" Margin="0,30,72,0" Name="textBox1" Text="{Binding Path=Rspchange, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True}" VerticalAlignment="Top" Width="75" />

and label:

<Label Content="{Binding Path= LF, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Height="24" HorizontalAlignment="Left" Margin="540,3,0,0" Name="lbLF" VerticalAlignment="Top" Width="84" />

Here I have used two way binding with property Rspchange and LF respectively.

public UInt16 Rspchange
    {
        get
        {
            return this.eObj.GetRsBaseline(this.index);
        }
        set
        {
                this.eObj.SetRsBaseline(value, this.Index);
                this.OnPropertyChanged(new PropertyChangedEventArgs("Rspchange"));
                this.eObj.writedata(DefaultFileName);
        }
    } 

public string LF
    {
        get
        {
            return this.eObj.LFrequency;
        }
        set
        {
            this.eObj.LFrequency = value;
            this.OnPropertyChanged(new PropertyChangedEventArgs(" LF"));
        }
    }

on mdel side I have this proerty like this:

public override string LFrequency
    {
        get { return configObject.lnFrequency.ToString(); }
        set { configObject.lnFrequency = Convert.ToByte(value); }
    }


public override UInt16 GetRsBaseline(int channelIndex)
    {

        return (byte)this.configObject.CConfig[index].Bline;
    }

public override void SetRsBaseline(UInt16 value, int index)
    {
        byte[] arr = BitConverter.GetBytes(value);
        this.configObject.CConfig[index].Bline = arr[0];
    }

public byte Bline
{
    get { return this.bline; }
    set { this.bline = value; }
}

public byte lnFrequency
    {
        get { return this.ln_frequency; }
        set { this.ln_frequency = value; }
    }

My application is communicating through serial port to other application. I'm getting data from other application and based on that I have to update my GUI as well.

When I debugged my code I have seen that I'm getting updated value from other application to ln_frequency and bline but it's not updating my GUI.

Please tell me what is problem with my code so that It can update my GUI once I get data from other application.

P.S: code of writexmldata

public void WriteXmlData(string path)

{

if ((ie.Current as XElement).Attribute("name").Value == "Bline")
            {
                (ie.Current as XElement).Attribute("value").Value = this.channel_config[0].Bline.ToString();
            }

if ((ie.Current as XElement).Attribute("name").Value == "LFrequency")
            {
                (ie.Current as XElement).Attribute("value").Value = this.lnFrequency.ToString();
            }

}

Here my intention is to save current value of Bline and LFrequency, so that when user will launch my application again user will get latest value on GUI all time.