Why struct doesn't work properly? : The Official Microsoft ASP.NET Forums

Mamba Dai - MSFT
Please post your project to the SkyDrive and you will get a shared reference, then please send it to my forum inbox by private message functionality.

Many thanks!

I'll do that.

Edited by ToughMan on Dec 10, 2012 06:26 AM
Edited by ToughMan on Dec 10, 2012 06:29 AM
Edited by ToughMan on Dec 10, 2012 06:32 AM
Edited by ToughMan on Dec 10, 2012 12:39 PM
Edited by ToughMan on Dec 16, 2012 07:15 AM
Edited by ToughMan on Dec 21, 2012 03:20 AM

Reply

Re: Why struct doesn't work properly?

Dec 08, 2012 05:31 AM|LINK

Hello MSFT,

Let me re-explain the problem again, please see it carefully and clearly, hope this clear you!

1) I have three kinds of files called "Point", "MyPoint" as well as a webpage. The first two files are of cs file (Class file):

[Point File]

namespace CSharp
{
    /// <summary>
    /// Todo: Please change "class" to "struct" first
    /// </summary>
    [TypeConverter(typeof(MyConvertor))]
    public class DPoint     {
        private double _x;
        private double _y;
        private double _z;
        [NotifyParentProperty(true)]
        public double Z
        {
            get { return _z; }
            set { _z = value; }
        }
        [NotifyParentProperty(true)]
        public double Y
        {
            get { return _y; }
            set { _y = value; }
        }
        [NotifyParentProperty(true)]
        public double X
        {
            get { return _x; }
            set { _x = value; }
        }
 
        public static explicit operator DPoint(string s)
        {
            string[] values = s.Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries);
            if (values.Length == 3)
            {
                double d = Convert.ToDouble(values[0]);
                double d2 = Convert.ToDouble(values[1]);
                double d3 = Convert.ToDouble(values[2]);
                DPoint dp = new DPoint { X = d, Y = d2, Z = d3 };
                return dp;
            }
            throw new Exception("Cannot do convert!");
        }
    }
    public class MyConvertor : ExpandableObjectConverter
    {
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            return typeof(string) == sourceType.GetType();
        }
 
        public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
        {
            return (DPoint)value.ToString();
        }
 
        public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)
        {
            if (value is DPoint)
            {
                DPoint dp = (DPoint)value;
                return string.Format("{0},{1},{2}", dp.X, dp.Y, dp.Z);
            }
            throw new Exception("Cannot do convert");
        }
        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            return destinationType.GetType() == typeof(string);
        }
        //public override bool GetStandardValuesSupported(ITypeDescriptorContext context)         //{         //    return true;         //}     }
}

[MyPoint file]

namespace CSharp
{
  [ParseChildren(true), PersistChildren(false)]
    public class MyDPoint : WebControl
    {
      DPoint dp = new DPoint();
 
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        [PersistenceMode(PersistenceMode.InnerProperty)]
        [NotifyParentProperty(true)]
        public DPoint DPoint
        {
            get
            {
                return dp;
            }
            set
            {
                dp = value;
            }
        }
 
        protected override void Render(HtmlTextWriter writer)
        {
            writer.Write(string.Format("[{0},{1},{2}]", DPoint.X, DPoint.Y, DPoint.Z));
        }
    }
}

[web file]

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="CSharp.WebForm1" %>
 
<%@ Register assembly="CSharp" namespace="CSharp" tagprefix="cc1" %>
 
<!DOCTYPE html>
 
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        
        <cc1:MyDPoint ID="MyDPoint1" runat="server">
<DPoint Z="0" Y="0" X="1"></DPoint>
        </cc1:MyDPoint>
        
    </div>
    </form>
</body>
</html>

Now my question is: PLEASE READ IT VERY CAREFULLY!!!!!!!!!!!!!!!!!!!!!!!

1) Plz directly copy my above codes and create several files to contain the proper codes.

Recompile them all and run ur project, And switch to Design mode of your web page and

DIRECTLY MODIFY THE VALUES IN THE PROPERTY PANEL of DPoint (X,Y,Z) values. Is everything OK?

2) Plz change from "class" in "Point" file to "struct", and then remove the control on the webpage and

re-create another new one by dragging and dropping onto the page itself, TRY TO MODIFY VALUES in the PROPERTY

PANEL FOR DPoint (X,Y,Z), You'll find you cannot modify, why?

Edited by ToughMan on Dec 10, 2012 06:26 AM
Edited by ToughMan on Dec 10, 2012 06:29 AM
Edited by ToughMan on Dec 10, 2012 06:32 AM
Edited by ToughMan on Dec 10, 2012 12:39 PM
Edited by ToughMan on Dec 16, 2012 07:15 AM
Edited by ToughMan on Dec 21, 2012 03:20 AM

Reply

Re: Why struct doesn't work properly?

Dec 10, 2012 06:25 AM|LINK

Hi,

ToughMan
Now my question is: PLEASE READ IT VERY CAREFULLY!!!!!!!!!!!!!!!!!!!!!!!

Again, I really check your reply carefully, and you initial reply provided the code is different now. You might notice it.

ToughMan
DIRECTLY MODIFY THE VALUES IN THE PROPERTY PANEL of DPoint (X,Y,Z) values. Is everything OK?

Yes, it's ok.

ToughMan

2) Plz change from "class" in "Point" file to "struct", and then remove the control on the webpage and

re-create another new one by dragging and dropping onto the page itself, TRY TO MODIFY VALUES in the PROPERTY

Can't modify the property.

Now try to explain the reason.

Firstly, you need to understand the difference between struct and class, please refer to below:

(Notice: it's important to understand the difference, it make you better to understand the both samples code at last)

http://msdn.microsoft.com/en-us/library/aa664471(v=vs.71).aspx

Now please modify the propeties with source code mode(in the web page) like below, since you couldn't modify it by properties window when using struct.

<cc1:MyDPoint ID="MyDPoint1" DPoint-X="1" DPoint-Y="3" DPoint-Z="4" runat="server">
</cc1:MyDPoint>

Run your web page, the error below will occur:

"Cannot modify the return value of 'CSharp.MyDPoint.DPoint' because it is not a variable "

That why you can't modify the properties.

(I assume you have read the reference above about difference between struct and class.)

and now have two samples below that sperately uses struct and class:

Using Struct:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Point point = new Point();
            point.X = 1;
            point.Y = 2;
            point.Z = 3;
            Console.WriteLine(point.X + ";" + point.Y + ";" + point.Z);
            MyClass myClass = new MyClass();
            myClass.Point1.X = 4;
            myClass.Point1.Y = 5;
            myClass.Point1.Z = 6;
            Console.WriteLine(myClass.Point1.X + ";" + myClass.Point1.Y + ";" + myClass.Point1.Z);

        }
    }
    class MyClass
    {
        Point point = new Point();
        public Point Point1
        {
            get
            {
                return point;
            }
            set
            {
                point = value;
            }
        }
    }
    struct  Point
    {
        private double _x;
        private double _y;
        private double _z;
        public double Z
        {
            get { return _z; }
            set { _z = value; }
        }
        public double Y
        {
            get { return _y; }
            set { _y = value; }
        }
        public double X
        {
            get { return _x; }
            set { _x = value; }
        }
    }
}

Using class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Point point = new Point();
            point.X = 1;
            point.Y = 2;
            point.Z = 3;
            Console.WriteLine(point.X + ";" + point.Y + ";" + point.Z);
            MyClass myClass = new MyClass();
            myClass.Point1.X = 4;
            myClass.Point1.Y = 5;
            myClass.Point1.Z = 6;
            Console.WriteLine(myClass.Point1.X + ";" + myClass.Point1.Y + ";" + myClass.Point1.Z);

        }
    }
    class MyClass
    {
        Point point = new Point();
        public Point Point1
        {
            get
            {
                return point;
            }
            set
            {
                point = value;
            }
        }
    }
    class  Point
    {
        private double _x;
        private double _y;
        private double _z;
        public double Z
        {
            get { return _z; }
            set { _z = value; }
        }
        public double Y
        {
            get { return _y; }
            set { _y = value; }
        }
        public double X
        {
            get { return _x; }
            set { _x = value; }
        }
    }
}

Run the both samples, you will find the sample using struct occurs one error as when you run the web page.

"Cannot modify the return value of 'CSharp.MyDPoint.DPoint' because it is not a variable "

"Cannot modify the return value of 'ConsoleApplication2.MyClass.Point1' because it is not a variable "

The both samples are better to explain why you couldn't modify the properties. Because when you create the

Because the CSharp.MyDPoint.DPoint just returns the copy of struct, and you were using it as reference(if class).

the copy of struct is like below:

            myClass.Point1.X = 0;
            myClass.Point1.Y = 0;
            myClass.Point1.Z = 0;

Because it's just a copy of struct, so when you modify the "X,Y,Z" like below:

<cc1:MyDPoint ID="MyDPoint1" DPoint-X="1" DPoint-Y="3" DPoint-Z="4" runat="server">
        </cc1:MyDPoint>

It's equal to do something like below:

0=1;
0=3;
0=4

But if you use the class, it would return one reference, obviously, you can modify it.

Please mark the replies as answers if they help or unmark if not.
Feedback to us

Develop and promote your apps in Windows Store

Edited by mamba dai - msft on Dec 10, 2012 06:26 AM
Edited by mamba dai - msft on Dec 10, 2012 06:26 AM
Edited by mamba dai - msft on Dec 10, 2012 06:29 AM
Edited by mamba dai - msft on Dec 10, 2012 06:29 AM
Edited by mamba dai - msft on Dec 10, 2012 06:32 AM
Edited by mamba dai - msft on Dec 10, 2012 06:32 AM
Edited by mamba dai - msft on Dec 10, 2012 12:39 PM
Edited by mamba dai - msft on Dec 16, 2012 07:15 AM
Edited by mamba dai - msft on Dec 21, 2012 03:20 AM

Reply

Re: Why struct doesn't work properly?

Dec 11, 2012 05:58 AM|LINK

Mamba Dai - MSFT
Mamba Dai - MSFT

Are u sure?

But if you uncomment the overridable method of:

public override bool GetStandardValuesSupported(ITypeDescriptorContext context)
{
return true;
}

Struct can also work!

Why?????????????????

Edited by ToughMan on Dec 16, 2012 07:15 AM
Edited by ToughMan on Dec 21, 2012 03:20 AM

Reply

Re: Why struct doesn't work properly?

Dec 14, 2012 07:56 AM|LINK

Hi,

ToughMan
Are u sure?

The explanation for the reason why can't modify the properties is right, but for why the properties can be modified after overriding GetStandardValuesSupported method, it may invovle some inner underground operations of .NET. The research for it is still processing.

Please mark the replies as answers if they help or unmark if not.
Feedback to us

Develop and promote your apps in Windows Store

Edited by mamba dai - msft on Dec 16, 2012 07:15 AM
Edited by mamba dai - msft on Dec 21, 2012 03:20 AM

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ToughMan

Participant

1490 Points

635 Posts

Re: Why struct doesn't work properly?

Dec 15, 2012 07:28 AM|LINK

Mamba Dai - MSFT
The research for it is still processing.

Many thanks, waiting for ur reply

Edited by ToughMan on Dec 16, 2012 07:15 AM
Edited by ToughMan on Dec 21, 2012 03:20 AM

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cts-mgraham

Contributor

3318 Points

642 Posts

Microsoft

Re: Why struct doesn't work properly?

Dec 15, 2012 12:09 PM|LINK

While reading through this I have to say that it took a little time to get my head around it, and I don't have an answer for you. By overriding the GetStandardValuesSupported and setting it to true, it seems you are basically bypassing one checkpoint the designer must use. I have sent a question over to our Languages team that understand these inner workings at a much lower level than I do. Hopefully, they will have some insight but this question may fall into the paid support category which requires a more in-depth level of support.

You can visit the below link to see the various paid support options that are available to better meet your needs. http://support.microsoft.com/default.aspx?id=fh;en-us;offerprophone

Michael Graham, MSFT

Edited by cts-mgraham on Dec 16, 2012 07:15 AM
Edited by cts-mgraham on Dec 21, 2012 03:20 AM

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ToughMan

Participant

1490 Points

635 Posts

Re: Why struct doesn't work properly?

Dec 16, 2012 01:53 AM|LINK

cts-mgraham
cts-mgraham

cts-mgraham

While reading through this I have to say that it took a little time to get my head around it, and I don't have an answer for you. By overriding the GetStandardValuesSupported and setting it to true, it seems you are basically bypassing one checkpoint the designer must use. I have sent a question over to our Languages team that understand these inner workings at a much lower level than I do. Hopefully, they will have some insight but this question may fall into the paid support category which requires a more in-depth level of support.

You can visit the below link to see the various paid support options that are available to better meet your needs. http://support.microsoft.com/default.aspx?id=fh;en-us;offerprophone

Man!

It seems that you Microsoft ONLY wanna money……I know that u Microsoft will go down……Right？

You cannot solve my problem but ONLY FOR MONEY……Why？

Edited by ToughMan on Dec 16, 2012 07:15 AM
Edited by ToughMan on Dec 16, 2012 07:15 AM
Edited by ToughMan on Dec 21, 2012 03:20 AM

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