CODEWITHSUNDEEP
c#xmlserializationdeserialization
Tereami
Tereami

Reputation: 5

C# deserialize a class - the "default" value of a variable

I save local user settings to xml file. Program contains "Settings" class that serialize when the program is closed and deserialize when it is started next time. But the problem is that the program is changed all the time, and when I create next version - I want the user settings to be saved. But the program may contains new fields of settings, and then the program will started and deserialised the old xml file - new fields will be null. Now I check every fields as hard-code in the program, as like:

Settings sts = (Settings)Deserialise(path);
if(sts.Field2 == null) sts.Field2 = "defaultvalue2";
if(sts.Field3 == null) sts.Field3 = "defaultvalue3";

Of course it is not satisfied for me. Is it possible to do "default" value of a variable as the same time when I change code of Settings class? Like this:

class Settings 
{
   public string Field1 (DefaultValue: "defaultvalue1");
   public string Field2 (DefaultValue: "defaultvalue2");
}
public void Main
{
   Settings sts = (Settings)Deserialise(path);
   foreach(var fld in typeof(sts))
   {
      if(fld.Value == null)
          fld.Value = Settings.Fields[fld].DefaulValue;
   }
}

Upvotes: 0

Views: 730

Answers (3)

Michael vd Berg
Michael vd Berg

Reputation: 42

The Settings.settings xml file was designed for static project settings and, using user scoped settings, can be saved at runtime. Are you changing the settings so much that it no longer have the 'old' values or just adding to the list of settings?

If just adding, you don't need to loop through the settings one by one and try to guess their types with values as you can just do this:

int myInteger = Properties.Settings.Default.MyIntegerSettingValue;

And writing to the settings file:

Properties.Settings.Default.MyIntegerSettingValue = myInteger;

So if you cannot replace your settings.xml file, my suggestion is to model your settings to a class that contain all of your settings loaded at runtime and for each one missing, just write it out to the Settings file with your default value:

Properties.Settings.Default.MyMissingSetting = "MyDefaultValue"

You can find some nice info on application settings usage here

Upvotes: 0

TimChang
TimChang

Reputation: 2417

https://learn.microsoft.com/zh-tw/dotnet/api/system.xml.serialization.xmlattributes.xmldefaultvalue?view=netcore-3.1

here I google it . maybe try it? Use default attribute : DefaultValueAttribute

public class Pet
{
   // The default value for the Animal field is "Dog".
   [DefaultValueAttribute("Dog")]
   public string Animal ;
}

Upvotes: 0

Sam Tigle
Sam Tigle

Reputation: 403

Yes it is possible, simply use the standard way to set standard values:

class Settings 
{
   public string Field1 = "defaultvalue1";
   public string Field2 = "defaultvalue2";
}
public void Main
{
   Settings sts = (Settings)Deserialise(path);
   /* not needed
   foreach(var fld in typeof(sts))
   {
      if(fld.Value == null)
          fld.Value = Settings.Fields[fld].DefaulValue;
   }*/
}

Upvotes: 1

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