Latitude And Longitude Keep Changing Every Time Convert From Degrees Minutes Seconds To Decimal Degrees In C#

If I enter the a location of: Latitude = 28 Degrees, 45 Minutes, 12 Seconds Longitude = 81 Degrees, 39 Minutes, 32.4 Seconds. It gets converted into Decimal Degrees format to be stored in the database with the following code:

Coordinates coordinates = new Coordinates();
coordinates.LatitudeDirection = this.radLatNorth.Checked ? Coordinates.Direction.North : Coordinates.Direction.South;
coordinates.LatitudeDegree = this.ConvertDouble(this.txtLatDegree.Text);
coordinates.LatitudeMinute = this.ConvertDouble(this.txtLatMinute.Text);
coordinates.LatitudeSecond = this.ConvertDouble(this.txtLatSecond.Text);
coordinates.LongitudeDirection = radLongEast.Checked ? Coordinates.Direction.East : Coordinates.Direction.West;
coordinates.LongitudeDegree = this.ConvertDouble(this.txtLongDegree.Text);
coordinates.LongitudeMinute = this.ConvertDouble(this.txtLongMinute.Text);
coordinates.LongitudeSecond = this.ConvertDouble(this.txtLongSecond.Text);
//gets the calulated fields of Lat and Long
coordinates.ConvertDegreesMinutesSeconds();
In the above code, ConvertDouble is defined as:
private double ConvertDouble(string value)
{
double newValue = 0;
double.TryParse(value, out newValue);
return newValue;
}
and ConvertDegreesMinutesSeconds is defined as:
public void ConvertDegreesMinutesSeconds()
{
this.Latitude = this.LatitudeDegree + (this.LatitudeMinute / 60) + (this.LatitudeSecond / 3600);
this.Longitude = this.LongitudeDegree + (this.LongitudeMinute / 60) + (this.LongitudeSecond / 3600);
//adds the negative sign
if (LatitudeDirection == Direction.South)
{
this.Latitude = 0 - this.Latitude;
}
else if (LongitudeDirection == Direction.West)
{
this.Longitude = 0 - this.Longitude;
}
}

If I don't make any change to the latitude or longitude and I click Apply Changes which basically does the above calucation again, it generates a different latitude and longitude in the database. This happens every time I go to edit it and don't make a change (I just click Apply Changes and it does the calculation again with a different result). In the above scenario, the new Latitude and Longitude is: Latitude = 28 Degrees, 45 Minutes, 12 Seconds Longitude = 81 Degrees, 40 Minutes, 32.4 Seconds If I do it again, it becomes:
Latitude = 28 Degrees, 45 Minutes, 12 Seconds Longitude = 81 Degrees, 41 Minutes, 32.4 Seconds The other part of this is that when I go into edit, it takes the decimal degrees format of the latitude and longitude and converts it to the degrees minutes seconds format and puts them into their respective textboxes. The code for that is:

public void SetFields()
{
Coordinates coordinateLocation = new Coordinates();
coordinateLocation.Latitude = this.Latitude;
coordinateLocation.Longitude = this.Longitude;
coordinateLocation.ConvertDecimal();
this.radLatNorth.Checked =
coordinateLocation.LatitudeDirection == Coordinates.Direction.North;
this.radLatSouth.Checked = !this.radLatNorth.Checked;
this.txtLatDegree.Text = coordinateLocation.LatitudeDegree.ToString().Replace("-", string.Empty);
this.txtLatMinute.Text = Math.Round(coordinateLocation.LatitudeMinute, 0).ToString().Replace("-", string.Empty);
this.txtLatSecond.Text = Math.Round(coordinateLocation.LatitudeSecond, 2).ToString().Replace("-", string.Empty);
this.radLongEast.Checked =
coordinateLocation.LongitudeDirection == Coordinates.Direction.East;
this.radLongWest.Checked = !this.radLongEast.Checked;
this.txtLongDegree.Text = coordinateLocation.LongitudeDegree.ToString().Replace("-", string.Empty); ;
this.txtLongMinute.Text = Math.Round(coordinateLocation.LongitudeMinute, 0).ToString().Replace("-", string.Empty);
this.txtLongSecond.Text = Math.Round(coordinateLocation.LongitudeSecond, 2).ToString().Replace("-", string.Empty);
}

From the above examples, you can see that the Minute kept increasing by 1, which would indicate why it is generating a different latitude and longitude in decimal degrees in the database, so I guess the problem is more in the above area, but I am not sure where or why it is doing it?

public void ConvertDecimal()
{
this.LatitudeDirection = this.Latitude > 0 ? Direction.North : Direction.South;
this.LatitudeDegree = (int)Math.Truncate(this.Latitude);
if (LatitudeDirection == Direction.South)
{
this.LatitudeDegree = 0 - this.LatitudeDegree;
}
this.LatitudeMinute = (this.Latitude - Math.Truncate(this.Latitude)) * 60;
this.LatitudeSecond = (this.LatitudeMinute - Math.Truncate(this.LatitudeMinute)) * 60;
this.LongitudeDirection = this.Longitude > 0 ? Direction.East : Direction.West;
this.LongitudeDegree = (int)Math.Truncate(this.Longitude);
if (LongitudeDirection == Direction.West)
{
this.LongitudeDegree = 0 - this.LongitudeDegree;
}
this.LongitudeMinute = (this.Longitude - Math.Truncate(this.Longitude)) * 60;
this.LongitudeSecond = (this.LongitudeMinute - Math.Truncate(this.LongitudeMinute)) * 60;
}