c# - Why doesn't Json.net properly serialize a class derived from TreeNode? -

i have class inherited treenode when try serialize returns string that's not json string (as expected).

for example:

string json = jsonconvert.serializeobject(new a()); 

output:

"treenode: " 

where a defined as:

public class : treenode { public int x { get; set; } } 

if remove treenode inheritance, output is:

{"x":0} 

why doesn't serialize property if it's inherited treenode? note: filter class serialize public properties of a class, using contract:

public class shouldserializecontractresolver : defaultcontractresolver {     private list<string> propertiesnames;      public shouldserializecontractresolver(type type)     {         this.propertiesnames =             type.getproperties(bindingflags.public | bindingflags.instance | bindingflags.declaredonly)             .select(p => p.name)             .tolist();     }      protected override jsonproperty createproperty(memberinfo member, memberserialization memberserialization)     {         jsonproperty property = base.createproperty(member, memberserialization);          property.shouldserialize =             instance =>             {                 return propertiesnames.contains(property.propertyname);             };          return property;     } } 

and serialize object using:

shouldserializecontractresolver contract = new shouldserializecontractresolver(typeof(customtreenode));             jsonserializersettings jsonserializersettings = new jsonserializersettings() { contractresolver = contract };             string json = jsonconvert.serializeobject(groups, formatting.indented, jsonserializersettings); 

but returns same invalid output mentioned in start of topic.

if you're talking system.windows.forms.treenode reason seeing behavior because treenode has [typeconverter] attribute applied it, causes json.net serialize simple string value instead of object.

you can work way want in couple of different ways.

1. apply [jsonobject] attribute custom treenode class

   [jsonobject] public class : treenode {      ... } 

2. or, override createcontract() method in custom contractresolver such explicitly creates object contract custom type:

   public class shouldserializecontractresolver : defaultcontractresolver {     private type mytype;     private list<string> propertiesnames;      public shouldserializecontractresolver(type type)     {         mytype = type;          this.propertiesnames =             type.getproperties(bindingflags.public | bindingflags.instance | bindingflags.declaredonly)             .select(p => p.name)             .tolist();     }      protected override jsoncontract createcontract(type objecttype)     {         if (objecttype == mytype)         {             return createobjectcontract(objecttype);         }         return base.createcontract(objecttype);     }      protected override jsonproperty createproperty(memberinfo member, memberserialization memberserialization)     {         jsonproperty property = base.createproperty(member, memberserialization);          property.shouldserialize =             instance =>             {                 return propertiesnames.contains(property.propertyname);             };          return property;     } }