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member hiding question

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  • L likefood

    I'm trying to make a visually reversed trackbar. For example, pretend the trackbar's value is 100 (out of 300). The public member "rValue" would tell you that the value is actually 200 (meaning Maximum - (Value - Minimum)). And, if the user set "rMaximum" to a certain value, it would adjust the Value accordingly (to keep it the same amount below Maximum, not the same amount above Minimum).

    -Daniel Typing too fast fro my owngood

    C Offline
    C Offline
    Christian Graus
    wrote on last edited by
    #4

    OK. Well, why not override the Value method instead and have it track in reverse ?

    Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

    L 1 Reply Last reply
    0
    • C Christian Graus

      OK. Well, why not override the Value method instead and have it track in reverse ?

      Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

      L Offline
      L Offline
      likefood
      wrote on last edited by
      #5

      Two responses... 1) Value is a method? I thought it was just an int member... I suppose it would be most efficient to make it one of those funky methods that look like members to outsiders, so that whenever it was changed the little tick thing would move... 2) If I try to override it, I can just call ((TrackBar)base).Value from inside my class, right? I'll give it a shot, thanks!

      -Daniel Typing too fast fro my owngood

      C 1 Reply Last reply
      0
      • L likefood

        Two responses... 1) Value is a method? I thought it was just an int member... I suppose it would be most efficient to make it one of those funky methods that look like members to outsiders, so that whenever it was changed the little tick thing would move... 2) If I try to override it, I can just call ((TrackBar)base).Value from inside my class, right? I'll give it a shot, thanks!

        -Daniel Typing too fast fro my owngood

        C Offline
        C Offline
        Christian Graus
        wrote on last edited by
        #6

        1 - OK, I mixed my terminology. I doubt it's an int. I meant it's a property. 2 - Yes, if you use new and not override, I'd expect you can do that.

        Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

        L 1 Reply Last reply
        0
        • C Christian Graus

          1 - OK, I mixed my terminology. I doubt it's an int. I meant it's a property. 2 - Yes, if you use new and not override, I'd expect you can do that.

          Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

          L Offline
          L Offline
          likefood
          wrote on last edited by
          #7

          Well, this is what I tried (code below). However, the compiler says "Use of keyword 'base' is not valid in this context". I thought that base was like this, but for accessing a parent class. How should I do it?

          public class ReverseTrackBar : TrackBar
          {
          private new int Value
          {
          get { return (((TrackBar)base).Maximum - (((TrackBar)base).Value - this.Minimum)); }
          set { ((TrackBar)base).Value = (((TrackBar)base).Maximum - ((int)value - this.Minimum)); }
          }
          private new int Maximum
          {
          get { return ((TrackBar)base).Maximum; }
          set
          {
          int val = this.Value;
          ((TrackBar)base).Maximum = (int)value;
          this.Value = val;
          }
          }
          public ReverseTrackBar()
          {
          this.Value = 0;
          }
          }

          -Daniel Typing too fast fro my owngood

          C L J 4 Replies Last reply
          0
          • L likefood

            Well, this is what I tried (code below). However, the compiler says "Use of keyword 'base' is not valid in this context". I thought that base was like this, but for accessing a parent class. How should I do it?

            public class ReverseTrackBar : TrackBar
            {
            private new int Value
            {
            get { return (((TrackBar)base).Maximum - (((TrackBar)base).Value - this.Minimum)); }
            set { ((TrackBar)base).Value = (((TrackBar)base).Maximum - ((int)value - this.Minimum)); }
            }
            private new int Maximum
            {
            get { return ((TrackBar)base).Maximum; }
            set
            {
            int val = this.Value;
            ((TrackBar)base).Maximum = (int)value;
            this.Value = val;
            }
            }
            public ReverseTrackBar()
            {
            this.Value = 0;
            }
            }

            -Daniel Typing too fast fro my owngood

            C Offline
            C Offline
            Christian Graus
            wrote on last edited by
            #8

            I guess the 'new' keyword is hiding the base value.

            Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

            L 1 Reply Last reply
            0
            • L likefood

              Well, this is what I tried (code below). However, the compiler says "Use of keyword 'base' is not valid in this context". I thought that base was like this, but for accessing a parent class. How should I do it?

              public class ReverseTrackBar : TrackBar
              {
              private new int Value
              {
              get { return (((TrackBar)base).Maximum - (((TrackBar)base).Value - this.Minimum)); }
              set { ((TrackBar)base).Value = (((TrackBar)base).Maximum - ((int)value - this.Minimum)); }
              }
              private new int Maximum
              {
              get { return ((TrackBar)base).Maximum; }
              set
              {
              int val = this.Value;
              ((TrackBar)base).Maximum = (int)value;
              this.Value = val;
              }
              }
              public ReverseTrackBar()
              {
              this.Value = 0;
              }
              }

              -Daniel Typing too fast fro my owngood

              L Offline
              L Offline
              likefood
              wrote on last edited by
              #9

              Oh, I guess you don't have to cast base to a type because the type is already known (the type I'm inheriting from).

              -Daniel Typing too fast fro my owngood

              C 1 Reply Last reply
              0
              • C Christian Graus

                I guess the 'new' keyword is hiding the base value.

                Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

                L Offline
                L Offline
                likefood
                wrote on last edited by
                #10

                No, that's not it. See the message I posted at the same time as you...

                -Daniel Typing too fast fro my owngood

                1 Reply Last reply
                0
                • L likefood

                  Oh, I guess you don't have to cast base to a type because the type is already known (the type I'm inheriting from).

                  -Daniel Typing too fast fro my owngood

                  C Offline
                  C Offline
                  Christian Graus
                  wrote on last edited by
                  #11

                  Yes, I wondered about that :-)

                  Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

                  1 Reply Last reply
                  0
                  • L likefood

                    Well, this is what I tried (code below). However, the compiler says "Use of keyword 'base' is not valid in this context". I thought that base was like this, but for accessing a parent class. How should I do it?

                    public class ReverseTrackBar : TrackBar
                    {
                    private new int Value
                    {
                    get { return (((TrackBar)base).Maximum - (((TrackBar)base).Value - this.Minimum)); }
                    set { ((TrackBar)base).Value = (((TrackBar)base).Maximum - ((int)value - this.Minimum)); }
                    }
                    private new int Maximum
                    {
                    get { return ((TrackBar)base).Maximum; }
                    set
                    {
                    int val = this.Value;
                    ((TrackBar)base).Maximum = (int)value;
                    this.Value = val;
                    }
                    }
                    public ReverseTrackBar()
                    {
                    this.Value = 0;
                    }
                    }

                    -Daniel Typing too fast fro my owngood

                    J Offline
                    J Offline
                    jjansen
                    wrote on last edited by
                    #12

                    Heritos Gger wrote:

                    However, the compiler says "Use of keyword 'base' is not valid in this context".

                    The error is not related to the use of the keyword 'base', but to the fact that you try to cast the base to type TrackBar. You don't need to do that. Remove all of these casts (e.g. ((TrackBar)base).Value should be base.Value) and the compiler error will disappear.

                    L 1 Reply Last reply
                    0
                    • L likefood

                      Well, this is what I tried (code below). However, the compiler says "Use of keyword 'base' is not valid in this context". I thought that base was like this, but for accessing a parent class. How should I do it?

                      public class ReverseTrackBar : TrackBar
                      {
                      private new int Value
                      {
                      get { return (((TrackBar)base).Maximum - (((TrackBar)base).Value - this.Minimum)); }
                      set { ((TrackBar)base).Value = (((TrackBar)base).Maximum - ((int)value - this.Minimum)); }
                      }
                      private new int Maximum
                      {
                      get { return ((TrackBar)base).Maximum; }
                      set
                      {
                      int val = this.Value;
                      ((TrackBar)base).Maximum = (int)value;
                      this.Value = val;
                      }
                      }
                      public ReverseTrackBar()
                      {
                      this.Value = 0;
                      }
                      }

                      -Daniel Typing too fast fro my owngood

                      J Offline
                      J Offline
                      jjansen
                      wrote on last edited by
                      #13

                      I think the solution to your problem is this: Hide the property of the base class, but make the access modifier the same as in the base class, i.e. public. Next, add the modifier protected to the set-accessor (.NET 2.0 required). The get-accessor cannot be protected as well, but I don't think that's a problem, I fact I think it's good practice to keep the get-accessor accessable. You'll get something like this: public new int Value { get { return (base.Maximum - (base.Value - this.Minimum)); } protected set { base.Value = base.Maximum - (value - this.Minimum); } } That should work.

                      L 1 Reply Last reply
                      0
                      • J jjansen

                        Heritos Gger wrote:

                        However, the compiler says "Use of keyword 'base' is not valid in this context".

                        The error is not related to the use of the keyword 'base', but to the fact that you try to cast the base to type TrackBar. You don't need to do that. Remove all of these casts (e.g. ((TrackBar)base).Value should be base.Value) and the compiler error will disappear.

                        L Offline
                        L Offline
                        likefood
                        wrote on last edited by
                        #14

                        Yes, you're right. I realized that, and now it works beautifully. http://www.codeproject.com/script/comments/forums.asp?forumid=1649&select=1719871&df=100&fr=70.5#xx1719871xx[^]

                        -Daniel Typing too fast fro my owngood

                        1 Reply Last reply
                        0
                        • J jjansen

                          I think the solution to your problem is this: Hide the property of the base class, but make the access modifier the same as in the base class, i.e. public. Next, add the modifier protected to the set-accessor (.NET 2.0 required). The get-accessor cannot be protected as well, but I don't think that's a problem, I fact I think it's good practice to keep the get-accessor accessable. You'll get something like this: public new int Value { get { return (base.Maximum - (base.Value - this.Minimum)); } protected set { base.Value = base.Maximum - (value - this.Minimum); } } That should work.

                          L Offline
                          L Offline
                          likefood
                          wrote on last edited by
                          #15

                          Yes, that's close to what I ended up with. The set accessor is fine to be public because I can perform the reversal of data right there. I just didn't want the "outside" to have access to the base class's Value and Maximum properties. All I needed to do was overload them with new, and now it works beautifully. Thank you, everyone! Case closed.

                          -Daniel Typing too fast fro my owngood

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