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Dynamically assign values to instance

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csharplinqperformancetutorialquestion
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  • 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

    C Offline
    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

      C 2 Replies Last reply
      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

        S 1 Reply Last reply
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        • C Calin Tatar

          I think you could try by using Dynamic Invocation. Calin

          S Offline
          S Offline
          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
            C Offline
            Calin Tatar
            wrote on last edited by
            #12

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

            1 Reply Last reply
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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

              S 1 Reply Last reply
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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

                D Offline
                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

                          S Offline
                          S Offline
                          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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                          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
                            #20

                            Also, you can use TypeDescriptor, and PropertyDescriptor. Calin

                            1 Reply Last reply
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