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Dynamically assign values to instance

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  • S S Senthil Kumar

    Zilo(svk) wrote:

    and I want to assing value to AClass.AValue without actually explicitly writing

    It's difficult to answer without knowing why. Is it because you don't know the type at compile time?

    Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

    S Offline
    S Offline
    Stevo Z
    wrote on last edited by
    #7

    Yes. I'm loading the class from dll as

    Assembly.LoadFile(string file);

    And I'd like to keep AClass as simple as possible, without any specific code to read or write values into it. It's just a data container.

    zilo

    S 1 Reply Last reply
    0
    • S Stevo Z

      Hi Guys, I'd like to dynamically assign values to a known class instance based on the Property name. An example describes perfectly what I want to do: There is a class

      public class AClass
      {
      public string _aValue;

          public string AValue
          {
              get { return \_aValue; }
              set { \_aValue = value; }
          }
      }
      

      and I want to assing value to AClass.AValue without actually explicitly writing:

      AClass aInstance = new AClass();
      aInstance.AValue = "value";

      and now comes the best part. I'd like to avoid reflection as much as possible, because performance matters. I could go and look for a property named "AValue" and do

      typeof(AClass).GetProperty("AValue").SetValue(aInstance, "value", null);

      however that's veery slow. It's got to be possible to do that some other way, Linq works like this and it's not slow. any ideas?

      zilo

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      C Offline
      Calin Tatar
      wrote on last edited by
      #8

      Basically, you are searching for an alternative to Reflection, right? Calin

      S 1 Reply Last reply
      0
      • C Calin Tatar

        Basically, you are searching for an alternative to Reflection, right? Calin

        S Offline
        S Offline
        Stevo Z
        wrote on last edited by
        #9

        Kind of. Something that does the job but keeps the speed on same level as direct access.

        zilo

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        0
        • S Stevo Z

          Kind of. Something that does the job but keeps the speed on same level as direct access.

          zilo

          C Offline
          C Offline
          Calin Tatar
          wrote on last edited by
          #10

          I think you could try by using Dynamic Invocation. Calin

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          • C Calin Tatar

            I think you could try by using Dynamic Invocation. Calin

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            Stevo Z
            wrote on last edited by
            #11

            Do you suggest to create a method using reflection on the fly:

            void AssingAValue(AClass aInstance, object value)
            {
            aInstance.AValue = value;
            }

            and then just call this method?

            zilo

            C 1 Reply Last reply
            0
            • S Stevo Z

              Do you suggest to create a method using reflection on the fly:

              void AssingAValue(AClass aInstance, object value)
              {
              aInstance.AValue = value;
              }

              and then just call this method?

              zilo

              C Offline
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              Calin Tatar
              wrote on last edited by
              #12

              yes, so you can dynamically change the AValue property. Calin

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              • S Stevo Z

                Yes. I'm loading the class from dll as

                Assembly.LoadFile(string file);

                And I'd like to keep AClass as simple as possible, without any specific code to read or write values into it. It's just a data container.

                zilo

                S Offline
                S Offline
                S Senthil Kumar
                wrote on last edited by
                #13

                Well, LINQ knows the types of data objects at compile time, so there's no similarity there. Without reflection, I guess your best bet is emitting the IL directly[^].

                Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

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                • S Stevo Z

                  Interesting idea, but... It's not only one, there will be many properties like this within AClass. And it needs to be done outside of constructor.

                  zilo

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                  D Offline
                  DaveyM69
                  wrote on last edited by
                  #14

                  Maybe extension methods could work. Create an extension method ToAClass for each type, and also pass the AClass instance.

                  public static class ExtensionMethods
                  {
                  static public void SetAClass(this string value, AClass instance)
                  {
                  instance.AString = value;
                  }

                  static public void SetAClass(this int value, AClass instance)
                  {
                      instance.AInt = value;
                  }
                  

                  }
                  public class AClass
                  {
                  public string AString
                  {
                  get;
                  set;
                  }
                  public int AInt
                  {
                  get;
                  set;
                  }
                  }

                  AClass aInstance = new AClass();
                  "Test string".SetAClass(aInstance);
                  123.SetAClass(aInstance);

                  Dave
                  BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
                  Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

                  S 1 Reply Last reply
                  0
                  • D DaveyM69

                    Maybe extension methods could work. Create an extension method ToAClass for each type, and also pass the AClass instance.

                    public static class ExtensionMethods
                    {
                    static public void SetAClass(this string value, AClass instance)
                    {
                    instance.AString = value;
                    }

                    static public void SetAClass(this int value, AClass instance)
                    {
                        instance.AInt = value;
                    }
                    

                    }
                    public class AClass
                    {
                    public string AString
                    {
                    get;
                    set;
                    }
                    public int AInt
                    {
                    get;
                    set;
                    }
                    }

                    AClass aInstance = new AClass();
                    "Test string".SetAClass(aInstance);
                    123.SetAClass(aInstance);

                    Dave
                    BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
                    Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

                    S Offline
                    S Offline
                    Stevo Z
                    wrote on last edited by
                    #15

                    Anyhow, whether is it extension methods or not, I'll have to create them dynamically using reflection and then just call those methods. I think I have a better idea now, thanks

                    zilo

                    1 Reply Last reply
                    0
                    • S S Senthil Kumar

                      Well, LINQ knows the types of data objects at compile time, so there's no similarity there. Without reflection, I guess your best bet is emitting the IL directly[^].

                      Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

                      S Offline
                      S Offline
                      Stevo Z
                      wrote on last edited by
                      #16

                      It doesn't have to, I'm using those classes to work with linq as well and it's working fine. Thanks for the suggestion, that looks to be the only way to go.

                      zilo

                      S 1 Reply Last reply
                      0
                      • S Stevo Z

                        It doesn't have to, I'm using those classes to work with linq as well and it's working fine. Thanks for the suggestion, that looks to be the only way to go.

                        zilo

                        S Offline
                        S Offline
                        S Senthil Kumar
                        wrote on last edited by
                        #17

                        Zilo(svk) wrote:

                        I'm using those classes to work with linq as well and it's working fine

                        Now I'm curious - can you paste a snippet of code that does that? I can't imagine LINQ working without you specifying the type somewhere (unless it's an anonymous type, of course).

                        Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

                        S 1 Reply Last reply
                        0
                        • S S Senthil Kumar

                          Zilo(svk) wrote:

                          I'm using those classes to work with linq as well and it's working fine

                          Now I'm curious - can you paste a snippet of code that does that? I can't imagine LINQ working without you specifying the type somewhere (unless it's an anonymous type, of course).

                          Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

                          S Offline
                          S Offline
                          Stevo Z
                          wrote on last edited by
                          #18

                          I ment the classes are not present withing the same solution or assembly when compiling the code. When working with linq, I'm using strong types. This is a sample of one of the classes:

                          [Table(Name = "Books")]
                          public partial class Book : IDALEntity
                          {
                          private int _BookId;
                          private string _Title;
                          private int _Price;
                          private int _PublisherID;

                              public Book()
                              {   }
                          
                              \[Column(Storage = "\_BookId", AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL", IsPrimaryKey = true)\]
                              public int BookId
                              {
                                  get
                                  {
                                      return this.\_BookId;
                                  }
                                  set
                                  {
                                     this.\_BookId = value;                 
                                  }
                              }
                          

                          ...
                          }

                          zilo

                          S 1 Reply Last reply
                          0
                          • S Stevo Z

                            I ment the classes are not present withing the same solution or assembly when compiling the code. When working with linq, I'm using strong types. This is a sample of one of the classes:

                            [Table(Name = "Books")]
                            public partial class Book : IDALEntity
                            {
                            private int _BookId;
                            private string _Title;
                            private int _Price;
                            private int _PublisherID;

                                public Book()
                                {   }
                            
                                \[Column(Storage = "\_BookId", AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL", IsPrimaryKey = true)\]
                                public int BookId
                                {
                                    get
                                    {
                                        return this.\_BookId;
                                    }
                                    set
                                    {
                                       this.\_BookId = value;                 
                                    }
                                }
                            

                            ...
                            }

                            zilo

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                            S Senthil Kumar
                            wrote on last edited by
                            #19

                            Well, LINQ uses reflection to read the custom attributes you provide for each property, so that it can map them to database columns. I guess they do it just once and then generate dynamic code to do the actual translation from SQL results to object property assignments.

                            Regards Senthil [MVP - Visual C#] _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro

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                            • S Stevo Z

                              Kind of. Something that does the job but keeps the speed on same level as direct access.

                              zilo

                              C Offline
                              C Offline
                              Calin Tatar
                              wrote on last edited by
                              #20

                              Also, you can use TypeDescriptor, and PropertyDescriptor. Calin

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