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Dynamically assign values to instance

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csharplinqperformancetutorialquestion
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  • D DaveyM69

    If it's only the one property you could use an implicit operator overload.

    public class AClass
    {
    public AClass() : this(string.Empty) { }
    private AClass(string aValue)
    {
    AValue = aValue;
    }
    public static implicit operator AClass(string aValue)
    {
    return new AClass(aValue);
    }
    public string AValue
    {
    get;
    set;
    }
    }

    AClass aInstance = "Test String";
    Console.WriteLine(aInstance.AValue);

    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
    #6

    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 1 Reply Last reply
    0
    • 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

          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
            0
            • C Calin Tatar

              I think you could try by using Dynamic Invocation. Calin

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

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

                1 Reply Last reply
                0
                • 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
                  0
                  • 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

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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

                              1 Reply Last reply
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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

                                1 Reply Last reply
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