Generic type conversion FROM string

Question

I have a class that I want to use to store  properties  for another class  These properties simply have a name and a value  Ideally  what I would like is to be able to add typed properties  so that the  value  returned is always of the type that I want it to be   The type should always be a primitive  This class subclasses an abstract class which basically stores the name and value as string  The idea being that this subclass will add some type-safety to the base class  as well as saving me on some conversion    So  I have created a class which is  roughly  this   public class TypedProperty lt DataType gt    Property       public DataType TypedValue               get      Having problems here            set   base Value   value ToString               So the question is   Is there a  generic  way to convert from string back to a primitive   I can t seem to find any generic interface that links the conversion across the board  something like ITryParsable would have been ideal

User · Answer

I used lobos answer and it works  But I had a problem with the conversion of doubles because of the culture settings  So I added  return  T Convert ChangeType base Value  typeof T   CultureInfo InvariantCulture

User · Answer

I am not sure whether I understood your intentions correctly  but let s see if this one helps   public class TypedProperty lt T gt    Property where T   IConvertible       public T TypedValue               get   return  T Convert ChangeType base Value  typeof T              set   base Value   value ToString

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For many types  integer  double  DateTime etc   there is a static Parse method  You can invoke it using reflection   MethodInfo m   typeof T  GetMethod  Parse   new Type     typeof string        if  m    null        return m Invoke null  new object     base Value

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You could possibly use a construct such as a traits class  In this way  you would have a parameterised helper class that knows how to convert a string to a value of its own type  Then your getter might look like this   get   return StringConverter lt DataType gt  FromString base Value       Now  I must point out that my experience with parameterised types is limited to C   and its templates  but I imagine there is some way to do the same sort of thing using C  generics

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lubos hasko s method fails for nullables   The method below will work for nullables   I didn t come up with it  though   I found it via Google   http   web archive org web 20101214042641 http   dogaoztuzun com post C-Generic-Type-Conversion aspx Credit to  Tuna Toksoz   Usage first     TConverter ChangeType lt T gt  StringValue       The class is below     public static class TConverter       public static T ChangeType lt T gt  object value                return  T ChangeType typeof T   value              public static object ChangeType Type t  object value                TypeConverter tc   TypeDescriptor GetConverter t           return tc ConvertFrom value              public static void RegisterTypeConverter lt T  TC gt    where TC   TypeConverter                TypeDescriptor AddAttributes typeof T   new TypeConverterAttribute typeof TC

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Yet another variation  Handles Nullables  as well as situations where the string is null and T is not nullable   public class TypedProperty lt T gt    Property where T   IConvertible       public T TypedValue               get                       if  base Value    null  return default T               var type   Nullable GetUnderlyingType typeof T      typeof T               return  T Convert ChangeType base Value  type                     set   base Value   value ToString

User · Answer

public class TypedProperty lt T gt    Property       public T TypedValue               get   return  T  object base Value            set   base Value   value ToString               I using converting via an object  It is a little bit simpler

User · Answer

You can do it in one line as below   YourClass obj    YourClass Convert ChangeType YourValue  typeof YourClass      Happy coding

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With inspiration from the Bob s answer  these extensions also support null value conversion and all primitive conversion back and fourth   public static class ConversionExtensions           public static object Convert this object value  Type t                        Type underlyingType   Nullable GetUnderlyingType t                if  underlyingType    null  amp  amp  value    null                                return null                            Type basetype   underlyingType    null   t   underlyingType              return System Convert ChangeType value  basetype                      public static T Convert lt T gt  this object value                        return  T value Convert typeof T                  Examples              string stringValue   null              int  intResult   stringValue Convert lt int  gt                  int  intValue   null              var strResult   intValue Convert lt string gt

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Check the static Nullable GetUnderlyingType  - If the underlying type is null  then the template parameter is not Nullable  and we can use that type directly - If the underlying type is not null  then use the underlying type in the conversion   Seems to work for me   public object Get  string  toparse  Type  t            Test for Nullable lt T gt  and return the base type instead      Type undertype   Nullable GetUnderlyingType  t       Type basetype   undertype    null    t   undertype      return Convert ChangeType  toparse  basetype      public T Get lt T gt  string  key        return  T Get  key  typeof T       public void test         int x   Get lt int gt   14        int  nx   Get lt Nullable lt int gt  gt   14

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TypeDescriptor GetConverter PropertyObject  ConvertFrom Value    TypeDescriptor is class having method GetConvertor which accept a Type object and then you can call ConvertFrom method to convert the value for that specified object

[c#] Generic type conversion FROM string

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