Setting a property by reflection with a string value

Question

I d like to set a property of an object through Reflection  with a value of type string  So  for instance  suppose I have a Ship class  with a property of Latitude  which is a double   Here s what I d like to do   Ship ship   new Ship    string value    5 5   PropertyInfo propertyInfo   ship GetType   GetProperty  Latitude    propertyInfo SetValue ship  value  null     As is  this throws an ArgumentException      Object of type  System String  cannot be converted to type  System Double     How can I convert value to the proper type  based on propertyInfo

User · Answer

I notice a lot of people are recommending Convert.ChangeType - This does work for some cases however as soon as you start involving nullable types you will start receiving InvalidCastExceptions:

http://weblogs.asp.net/pjohnson/archive/2006/02/07/Convert.ChangeType-doesn_2700_t-handle-nullables.aspx

A wrapper was written a few years ago to handle this but that isn't perfect either.

http://weblogs.asp.net/pjohnson/archive/2006/02/07/Convert.ChangeType-doesn_2700_t-handle-nullables.aspx

User · Answer

You re probably looking for the Convert ChangeType method  For example   Ship ship   new Ship    string value    5 5   PropertyInfo propertyInfo   ship GetType   GetProperty  Latitude    propertyInfo SetValue ship  Convert ChangeType value  propertyInfo PropertyType   null

User · Answer

Or you could try   propertyInfo SetValue ship  Convert ChangeType value  propertyInfo PropertyType   null      But this will cause problems if your string value IsNullOrEmplty

User · Answer

As several others have said  you want to use Convert ChangeType   propertyInfo SetValue ship      Convert ChangeType value  propertyInfo PropertyType       null     In fact  I recommend you look at the entire Convert Class   This class  and many other useful classes are part of the System Namespace  I find it useful to scan that namespace every year or so to see what features I ve missed  Give it a try

User · Answer

You can use Convert ChangeType   - It allows you to use runtime information on any IConvertible type to change representation formats  Not all conversions are possible  though  and you may need to write special case logic if you want to support conversions from types that are not IConvertible   The corresponding code  without exception handling or special case logic  would be   Ship ship   new Ship    string value    5 5   PropertyInfo propertyInfo   ship GetType   GetProperty  Latitude    propertyInfo SetValue ship  Convert ChangeType value  propertyInfo PropertyType   null

User · Answer

I tried the answer from LBushkin and it worked great  but it won t work for null values and nullable fields  So I ve changed it to this   propertyName   Latitude   PropertyInfo propertyInfo   ship GetType   GetProperty propertyName   if  propertyInfo    null         Type t   Nullable GetUnderlyingType propertyInfo PropertyType     propertyInfo PropertyType       object safeValue    value    null    null   Convert ChangeType value  t        propertyInfo SetValue ship  safeValue  null

User · Answer

I will answer this with a general answer  Usually these answers not working with guids  Here is a working version with guids too   var stringVal  6e3ba183-89d9-e611-80c2-00155dcfb231      guid value as string to set var prop   obj GetType   GetProperty  FooGuidProperty       property to be setted var propType   prop PropertyType      var will be type of guid here var valWithRealType   TypeDescriptor GetConverter propType  ConvertFrom stringVal

User · Answer

If you are writing Metro app  you should use other code   Ship ship   new Ship    string value    5 5   PropertyInfo propertyInfo   ship GetType   GetTypeInfo   GetDeclaredProperty  Latitude    propertyInfo SetValue ship  Convert ChangeType value  propertyInfo PropertyType      Note   ship GetType   GetTypeInfo   GetDeclaredProperty  Latitude      instead of  ship GetType   GetProperty  Latitude

User · Answer

You can use a type converter  no error checking    Ship ship   new Ship    string value    5 5   var property   ship GetType   GetProperty  Latitude    var convertedValue   property Converter ConvertFrom value   property SetValue self  convertedValue     In terms of organizing the code  you could create a kind-of mixin that would result in code like this   Ship ship   new Ship    ship SetPropertyAsString  Latitude    5 5      This would be achieved with this code   public interface MPropertyAsStringSettable     public static class PropertyAsStringSettable     public static void SetPropertyAsString      this MPropertyAsStringSettable self  string propertyName  string value        var property   TypeDescriptor GetProperties self  propertyName       var convertedValue   property Converter ConvertFrom value       property SetValue self  convertedValue          public class Ship   MPropertyAsStringSettable     public double Latitude   get  set                 MPropertyAsStringSettable can be reused for many different classes   You can also create your own custom type converters to attach to your properties or classes   public class Ship   MPropertyAsStringSettable     public Latitude Latitude   get  set                 TypeConverter typeof LatitudeConverter    public class Latitude

User · Answer

Using the following code should solve your issue   item SetProperty prop Name  Convert ChangeType item GetProperty prop Name  ToString   Trim    prop PropertyType

User · Answer

Using Convert ChangeType and getting the type to convert from the PropertyInfo PropertyType   propertyInfo SetValue  ship                         Convert ChangeType  value  propertyInfo PropertyType                           null

User · Answer

Are you looking to play around with Reflection or are you looking to build a production piece of software   I would question why you re using reflection to set a property   Double new latitude   Double TryParse  value  out new latitude   ship Latitude   new latitude

[c#] Setting a property by reflection with a string value

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