Get property value from string using reflection

Question

I am trying implement the Data transformation using Reflection1 example in my code   The GetSourceValue function has a switch comparing various types  but I want to remove these types and properties and have GetSourceValue get the value of the property using only a single string as the parameter   I want to pass a class and property in the string and resolve the value of the property   Is this possible   1 Web Archive version of original blog post

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public static List lt KeyValuePair lt string  string gt  gt  GetProperties object item    where T   class               var result   new List lt KeyValuePair lt string  string gt  gt             if  item    null                        var type   item GetType                var properties   type GetProperties BindingFlags Public   BindingFlags Instance               foreach  var pi in properties                                var selfValue   type GetProperty pi Name  GetValue item  null                   if  selfValue    null                                        result Add new KeyValuePair lt string  string gt  pi Name  selfValue ToString                                        else                                       result Add new KeyValuePair lt string  string gt  pi Name  null                                                      return result          This is a way to get all properties with their values in a List

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You never mention what object you are inspecting  and since you are rejecting ones that reference a given object  I will assume you mean a static one   using System Reflection  public object GetPropValue string prop        int splitPoint   prop LastIndexOf           Type type   Assembly GetEntryAssembly   GetType prop Substring 0  splitPoint        object obj   null      return type GetProperty prop Substring splitPoint   1   GetValue obj  null       Note that I marked the object that is being inspected with the local variable obj  null means static  otherwise set it to what you want  Also note that the GetEntryAssembly   is one of a few available methods to get the  running  assembly  you may want to play around with it if you are having a hard time loading the type

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Great answer by jheddings  I would like to improve it by allowing referencing of aggregated arrays or collections of objects  so that propertyName could be property1 property2 X  property3      public static object GetPropertyValue object srcobj  string propertyName                if  srcobj    null              return null           object obj   srcobj              Split property name to parts  propertyName could be hierarchical  like obj subobj subobj property         string   propertyNameParts   propertyName Split                foreach  string propertyNamePart in propertyNameParts                        if  obj    null     return null                  propertyNamePart could contain reference to specific                 element  by index  inside a collection             if   propertyNamePart Contains  quot   quot                                  PropertyInfo pi   obj GetType   GetProperty propertyNamePart                   if  pi    null  return null                  obj   pi GetValue obj  null                             else                    propertyNamePart is areference to specific element                      by index  inside a collection                    like AggregatedCollection 123                       get collection name and element index                 int indexStart   propertyNamePart IndexOf  quot   quot   1                  string collectionPropertyName   propertyNamePart Substring 0  indexStart-1                   int collectionElementIndex   Int32 Parse propertyNamePart Substring indexStart  propertyNamePart Length-indexStart-1                         get collection object                 PropertyInfo pi   obj GetType   GetProperty collectionPropertyName                   if  pi    null  return null                  object unknownCollection   pi GetValue obj  null                        try to process the collection as array                 if  unknownCollection GetType   IsArray                                        object   collectionAsArray   unknownCollection as object                        obj   collectionAsArray collectionElementIndex                                     else                                            try to process the collection as IList                     System Collections IList collectionAsList   unknownCollection as System Collections IList                      if  collectionAsList    null                                                obj   collectionAsList collectionElementIndex                                             else                                                      Unsupported collection type                                                                          return obj

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Add to any Class   public class Foo       public object this string propertyName                get   return this GetType   GetProperty propertyName  GetValue this  null             set   this GetType   GetProperty propertyName  SetValue this  value  null                public string Bar   get  set        Then  you can use as   Foo f   new Foo       Set f  Bar      asdf      Get string s    string f  Bar

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Dim NewHandle As YourType   CType Microsoft VisualBasic CallByName ObjectThatContainsYourVariable   YourVariableName   CallType   YourType

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The below method works perfect for me   class MyClass       public string prop1   set  get         public object this string propertyName                get   return this GetType   GetProperty propertyName  GetValue this  null             set   this GetType   GetProperty propertyName  SetValue this  value  null               To get the property value   MyClass t1   new MyClass        string value   t1  prop1   ToString      To set the property value   t1  prop1     value

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Here is another way to find a nested property that doesn t require the string to tell you the nesting path  Credit to Ed S  for the single property method       public static T FindNestedPropertyValue lt T  N gt  N model  string propName            T retVal   default T           bool found   false           PropertyInfo   properties   typeof N  GetProperties             foreach  PropertyInfo property in properties                var currentProperty   property GetValue model  null                if   found                    try                       retVal   GetPropValue lt T gt  currentProperty  propName                       found   true                    catch                                      if   found                throw new Exception  Unable to find property      propName                      return retVal                 public static T GetPropValue lt T gt  object srcObject  string propName            return  T srcObject GetType   GetProperty propName  GetValue srcObject  null

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The following code is a Recursive method for displaying the entire hierarchy  of all of the Property Names and Values contained in an object s instance   This method uses a simplified version of AlexD s GetPropertyValue   answer above in this thread   Thanks to this discussion thread  I was able to figure out how to do this   For example  I use this method to show an explosion or dump of all of the properties in a WebService response by calling the method as follows       PropertyValues byRecursion  Response   response  false     public static object GetPropertyValue object srcObj  string propertyName      if  srcObj    null           return null         PropertyInfo pi   srcObj GetType   GetProperty propertyName Replace               if  pi    null          return null        return pi GetValue srcObj      public static void PropertyValues byRecursion string parentPath  object parentObj  bool showNullValues          Processes all of the objects contained in the parent object          If an object has a Property Value  then the value is written to the Console         Else if the object is a container  then this method is called recursively             using the current path and current object as parameters       Note   If you do not want to see null values  set showNullValues   false    foreach  PropertyInfo pi in parentObj GetType   GetTypeInfo   GetProperties               Build the current object property s namespace path           Recursion extends this to be the property s full namespace path      string currentPath   parentPath         pi Name          Get the selected property s value as an object     object myPropertyValue   GetPropertyValue parentObj  pi Name       if  myPropertyValue    null                 Instance of Property does not exist       if  showNullValues                  Console WriteLine currentPath       null               Note  If you are replacing these Console Write    methods callback methods                   consider passing DBNull Value instead of null in any method object parameters                    else if  myPropertyValue GetType   IsArray                 myPropertyValue is an object instance of an Array of business objects           Initialize an array index variable so we can show NamespacePath idx  in the results        int idx   0        foreach  object business in  Array myPropertyValue                  if  business    null                         Instance of Property does not exist              Not sure if this is possible in this context            if  showNullValues                          Console WriteLine currentPath          idx ToString               null                                  else if  business GetType   IsArray                         myPropertyValue idx  is another Array               Let recursion process it            PropertyValues byRecursion currentPath         idx ToString          business  showNullValues                     else if  business GetType   IsSealed                         Display the Full Property Path and its Value           Console WriteLine currentPath         idx ToString              business ToString                       else                        Unsealed Type Properties can contain child objects               Recurse into my property value object to process its properties and child objects            PropertyValues byRecursion currentPath         idx ToString          business  showNullValues                     idx                      else if  myPropertyValue GetType   IsSealed                 myPropertyValue is a simple value       Console WriteLine currentPath           myPropertyValue ToString               else                Unsealed Type Properties can contain child objects           Recurse into my property value object to process its properties and child objects        PropertyValues byRecursion currentPath  myPropertyValue  showNullValues

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public static object GetPropValue object src  string propName          return src GetType   GetProperty propName  GetValue src  null        Of course  you will want to add validation and whatnot  but that is the gist of it

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What about using the CallByName of the Microsoft VisualBasic namespace  Microsoft VisualBasic dll   It uses reflection to get properties  fields  and methods of normal objects  COM objects  and even dynamic objects   using Microsoft VisualBasic  using Microsoft VisualBasic CompilerServices    and then  Versioned CallByName this   method function prop name   CallType Get  ToString

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public class YourClass         Add below line in your class     public object this string propertyName    gt  GetType   GetProperty propertyName   GetValue this  null       public string SampleProperty   get  set         And you can get value of any property like this  var value   YourClass  SampleProperty

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Here s what I got based on other answers  A little overkill on getting so specific with the error handling   public static T GetPropertyValue lt T gt  object sourceInstance  string targetPropertyName  bool throwExceptionIfNotExists   false        string errorMsg   null       try               if  sourceInstance    null    string IsNullOrWhiteSpace targetPropertyName                         errorMsg     Source object is null or property name is null or whitespace    targetPropertyName                 Log Warn errorMsg                if  throwExceptionIfNotExists                  throw new ArgumentException errorMsg               else                 return default T                      Type returnType   typeof T           Type sourceType   sourceInstance GetType             PropertyInfo propertyInfo   sourceType GetProperty targetPropertyName  returnType           if  propertyInfo    null                        errorMsg     Property name   targetPropertyName   of type   returnType   not found for source object of type   sourceType                 Log Warn errorMsg                if  throwExceptionIfNotExists                  throw new ArgumentException errorMsg               else                 return default T                      return  T propertyInfo GetValue sourceInstance  null             catch Exception ex                errorMsg     Problem getting property name   targetPropertyName   from source instance            Log Error errorMsg  ex            if  throwExceptionIfNotExists              throw             return default T

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shorter way       var a   new Test   Id   1   Name    A    date   DateTime Now   var b   new Test   Id   1   Name    AXXX   date   DateTime Now     var compare   string Join    a GetType   GetProperties   Select x   gt  x GetValue a   ToArray                    string Join    b GetType   GetProperties   Select x   gt  x GetValue b   ToArray

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Using PropertyInfo of the System Reflection namespace  Reflection compiles just fine no matter what property we try to access  The error will come up during run-time        public static object GetObjProperty object obj  string property                Type t   obj GetType            PropertyInfo p   t GetProperty  Location            Point location    Point p GetValue obj  null           return location          It works fine to get the Location property of an object  Label1 Text   GetObjProperty button1   Location   ToString      We ll get the Location    X 71 Y 27  We can also return location X or location Y on the same way

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About the nested properties discussion  you can avoid all the reflection stuff if you use the DataBinder Eval Method  Object  String  as below   var value   DataBinder Eval DateTime Now   TimeOfDay Hours      Of course  you ll need to add a reference to the System Web assembly  but this probably isn t a big deal

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jheddings and AlexD both wrote excellent answers on how to resolve property strings  I d like to throw mine in the mix  since I wrote a dedicated library exactly for that purpose   Pather CSharp s main class is Resolver  Per default it can resolve properties  array and dictionary entries   So  for example  if you have an object like this  var o   new   Property1   new   Property2    value         and want to get Property2  you can do it like this   IResolver resolver   new Resolver    var path    Property1 Property2   object result   r Resolve o  path        gt   value    This is the most basic example of the paths it can resolve  If you want to see what else it can  or how you can extend it  just head to its Github page

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public static TValue GetFieldValue lt TValue gt  this object instance  string name        var type   instance GetType         var field   type GetFields BindingFlags NonPublic   BindingFlags Static   BindingFlags Instance  FirstOrDefault e   gt  typeof TValue  IsAssignableFrom e FieldType   amp  amp  e Name    name       return  TValue field  GetValue instance      public static TValue GetPropertyValue lt TValue gt  this object instance  string name        var type   instance GetType        var field   type GetProperties BindingFlags NonPublic   BindingFlags Static   BindingFlags Instance  FirstOrDefault e   gt  typeof TValue  IsAssignableFrom e PropertyType   amp  amp  e Name    name       return  TValue field  GetValue instance

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How about something like this   public static Object GetPropValue this Object obj  String name        foreach  String part in name Split                 if  obj    null    return null             Type type   obj GetType            PropertyInfo info   type GetProperty part           if  info    null    return null             obj   info GetValue obj  null             return obj     public static T GetPropValue lt T gt  this Object obj  String name        Object retval   GetPropValue obj  name       if  retval    null    return default T             throws InvalidCastException if types are incompatible     return  T  retval      This will allow you to descend into properties using a single string  like this   DateTime now   DateTime Now  int min   GetPropValue lt int gt  now   TimeOfDay Minutes    int hrs   now GetPropValue lt int gt   TimeOfDay Hours      You can either use these methods as static methods or extensions

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Here is my solution  It works also with COM objects and allows to access collection array items from COM objects   public static object GetPropValue this object obj  string name        foreach  string part in name Split                     if  obj    null    return null             Type type   obj GetType            if  type Name       ComObject                         if  part Contains                                     string partWithoundIndex   part                  int index   ParseIndexFromPropertyName ref partWithoundIndex                   obj   Versioned CallByName obj  partWithoundIndex  CallType Get  index                             else                               obj   Versioned CallByName obj  part  CallType Get                                   else                       PropertyInfo info   type GetProperty part               if  info    null    return null                obj   info GetValue obj  null                       return obj     private static int ParseIndexFromPropertyName ref string name        int index   -1      int s   name IndexOf        1      int e   name IndexOf           if  e  lt  s                throw new ArgumentException              string tmp   name Substring s  e - s       index   Convert ToInt32 tmp       name   name Substring 0  s - 1       return index

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If I use the code from Ed S  I get      ReflectionExtensions GetProperty Type  string   is inaccessible due to its protection level   It seems that GetProperty   is not available in Xamarin Forms  TargetFrameworkProfile is Profile7 in my Portable Class Library   NET Framework 4 5  Windows 8  ASP NET Core 1 0  Xamarin Android  Xamarin iOS  Xamarin iOS Classic    Now I found a working solution   using System Linq  using System Reflection   public static object GetPropValue object source  string propertyName        var property   source GetType   GetRuntimeProperties   FirstOrDefault p   gt  string Equals p Name  propertyName  StringComparison OrdinalIgnoreCase        return property  GetValue source       Source

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Have a look at the Heleonix Reflection library  You can get set invoke members by paths  or create a getter setter  lambda compiled into a delegate  which is faster than reflection  For example   var success   Reflector Get DateTime Now  null   Date Year   out int value     Or create a getter once and cache for reuse  this is more performant but might throw NullReferenceException if an intermediate member is null    var getter   Reflector CreateGetter lt DateTime  int gt   Date Year   typeof DateTime    getter DateTime Now     Or if you want to create a List lt Action lt object  object gt  gt  of different getters  just specify base types for compiled delegates  type conversions will be added into compiled lambdas    var getter   Reflector CreateGetter lt object  object gt   Date Year   typeof DateTime    getter DateTime Now

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The method to call has changed in  NET Standard  as of 1 6   Also we can use C  6 s null conditional operator   using System Reflection   public static object GetPropValue object src  string propName        return src GetType   GetRuntimeProperty propName   GetValue src

[c#] Get property value from string using reflection

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