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The short answer to this is that IEnumerable<T> also mandates that you implement IEnumerable, which requires a method of signature
IEnumerator GetEnumerator()
Fortunately IEnumerator<T> similarly mandates IEnumerator, so you can fulfil this contract with an explicit interface implementation:
IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
(If you need to write an enumerator yourself, there's a similar issue with the Current property in IEnumerator<T> and IEnumerator, and a similar fix to return the same value but cast to object.)
However, as already pointed out, your graph is essentially wrapping a NodeList, and that already implements IEnumerable<T>. Instead of making an intermediate iterator, why not just forward the interface methods directly to the inner list?
IEnumerator<T> IEnumerable<T>.GetEnumerator() { return nodeList.GetEnumerator(); }
IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
(I've done both as explicit for symmetry and because you shouldn't be calling GetEnumerator directly; only one of them needs to be explicit.)
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Dear Sir,
I had tried your kind suggestion ,but unfortunately faild as shown below.please could you help me by making the changes on the following code segment and returned it to me “I’m very sorry to bother you………”
Error 3 foreach statement cannot operate on variables of type 'WindowsApplication4.NodeList<t>' because 'WindowsApplication4.NodeList<t>' does not contain a public definition for 'GetEnumerator'
namespace WindowsApplication4
{
///
/// Represents a graph. A graph is an arbitrary collection of GraphNode
instances.
///
/// <typeparam name="T">The type of data stored in the graph's
nodes.
public class Graph<t> : IEnumerable<t>
{
#region Private Member Variables
private NodeList<t> nodeSet; // the set of nodes in the graph
#endregion
#region Constructors
public Graph() : this(null) { }
public Graph(NodeList<t> nodeSet)
{
if (nodeSet == null)
this.nodeSet = new NodeList<t>();
else
this.nodeSet = nodeSet;
}
#endregion
#region Methods
#region Add
#region AddNode
///
/// Adds a new GraphNode instance to the Graph
///
/// <param name="node" />The GraphNode instance to add.
///
#region IEnumerable<t> Members
///
/// Returns an enumerator that allows for iterating through the
contents of the graph.
public IEnumerator<t> GetEnumerator()
{
foreach (GraphNode<t> gnode in nodeSet)
yield return gnode.Value;
}
#endregion
////////////////////////////////////////////////////////////
IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
public void AddNode(GraphNode<t> node)
{
// adds a node to the graph
nodeSet.Add(node);
}
///
/// Adds a new value to the graph.
///
/// <param name="value" />The value to add to the graph
public void AddNode(T value)
{
nodeSet.Add(new GraphNode<t>(value));
}
#endregion
#region Add*Edge Methods
///
/// Adds a directed edge from a GraphNode with one value (from) to a GraphNode with another value (to).
///
/// <param name="from" />The value of the GraphNode from which the directed edge eminates.
/// <param name="to" />The value of the GraphNode to which the edge leads.
public void AddDirectedEdge(T from, T to)
{
AddDirectedEdge(from, to, 0);
}
and if I Changed it to public like this
public IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
Error 1 The modifier 'public' is not valid for this item
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I assumed that NodeList inherited from List<T>. If it is a custom class, firstly, it probably shouldn't be (it is a list, it should be a List<Node<T>> unless there's a good reason for it not to be), and secondly, it must itself implement IEnumerable<T> as you are trying to foreach over it in the GetEnumerator method.
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Dear BobJanova,
Agian sorry to bother you,
I would like to inform your highness I'm using
Visual Studio 2005 C# and Vista home Basic edition OS ,if they have some effects.
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Hello experts,
even though I tried to create a minimal code sample, this question needs rather large code samples attached. Don't worry, all the interesting text is here, above all the code.
An application has to serialize data to a file and to de-serialize from that file. This works like a charm. The working example is attached in the first two code samples.
Now for the interesting part: the original working version is delivered to millions of satisfied customers. All their positive feedback encouraged the creation of version 2. Version 2 should of course be able to load data files from version 1. It is possible to change the data model without breaking compatibility, to some extend at least using ObsoleteAttribute and OptionalFieldAttribute. But when changes get more fundamental, other approaches are to be researched.
The third code sample shows an altered <cdoe>DataContainer class. In this example, it has to serialize one field that is not present in the original version. Therefore the well-known loading process fails.
To recover from the exception, another assembly is loaded. In my test case, it's the original assembly. It's delivered within the version 2 project resources.
The original assembly should load the legacy file. But it throws a TargetInvocationException instead. Its inner exception tells us that DataContainer has three members while there are only two de-serialized.
Now where does this legacy assembly know of DataContainer having three members nowadays?
It should have called its integrated version of DataContainer, which then had two members and therefore should load the legacy file without moaning.
However, here is the "minimal" working sample:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace Test_Serialization_Versioning_Heavy
{
public partial class Form1 : Form
{
#region Declarations
string _filename = string.Empty;
DataContainer _dataContainer = new DataContainer();
#endregion
#region Init
public Form1()
{
_filename = System.IO.Path.Combine(Application.StartupPath, "datafile.xml");
InitializeComponent();
ShowData();
}
#endregion
#region User Interaction
private void btLoad_Click(object sender, EventArgs e)
{
_dataContainer = DataContainer.LoadDataContainter(_filename);
ShowData();
}
private void btSave_Click(object sender, EventArgs e)
{
_dataContainer.Save(_filename);
}
#endregion
private void ShowData()
{
pgData.SelectedObject = _dataContainer;
}
#region Vom Windows Form-Designer generierter Code
private System.ComponentModel.IContainer components = null;
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
private void InitializeComponent()
{
this.tlpMain = new System.Windows.Forms.TableLayoutPanel();
this.btLoad = new System.Windows.Forms.Button();
this.btSave = new System.Windows.Forms.Button();
this.pgData = new System.Windows.Forms.PropertyGrid();
this.tlpMain.SuspendLayout();
this.SuspendLayout();
this.tlpMain.ColumnCount = 3;
this.tlpMain.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Absolute, 96F));
this.tlpMain.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Absolute, 96F));
this.tlpMain.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Percent, 100F));
this.tlpMain.Controls.Add(this.btLoad, 0, 0);
this.tlpMain.Controls.Add(this.btSave, 1, 0);
this.tlpMain.Controls.Add(this.pgData, 0, 1);
this.tlpMain.Dock = System.Windows.Forms.DockStyle.Fill;
this.tlpMain.Location = new System.Drawing.Point(0, 0);
this.tlpMain.Name = "tlpMain";
this.tlpMain.RowCount = 2;
this.tlpMain.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Absolute, 35F));
this.tlpMain.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 100F));
this.tlpMain.Size = new System.Drawing.Size(386, 392);
this.tlpMain.TabIndex = 0;
this.btLoad.Anchor = System.Windows.Forms.AnchorStyles.None;
this.btLoad.Location = new System.Drawing.Point(10, 6);
this.btLoad.Name = "btLoad";
this.btLoad.Size = new System.Drawing.Size(75, 23);
this.btLoad.TabIndex = 0;
this.btLoad.Text = "Load";
this.btLoad.UseVisualStyleBackColor = true;
this.btLoad.Click += new System.EventHandler(this.btLoad_Click);
this.btSave.Anchor = System.Windows.Forms.AnchorStyles.None;
this.btSave.Location = new System.Drawing.Point(106, 6);
this.btSave.Name = "btSave";
this.btSave.Size = new System.Drawing.Size(75, 23);
this.btSave.TabIndex = 1;
this.btSave.Text = "Save";
this.btSave.UseVisualStyleBackColor = true;
this.btSave.Click += new System.EventHandler(this.btSave_Click);
this.tlpMain.SetColumnSpan(this.pgData, 3);
this.pgData.Dock = System.Windows.Forms.DockStyle.Fill;
this.pgData.Location = new System.Drawing.Point(3, 38);
this.pgData.Name = "pgData";
this.pgData.Size = new System.Drawing.Size(380, 351);
this.pgData.TabIndex = 2;
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(386, 392);
this.Controls.Add(this.tlpMain);
this.Name = "Form1";
this.Text = "Form1";
this.tlpMain.ResumeLayout(false);
this.ResumeLayout(false);
}
private System.Windows.Forms.TableLayoutPanel tlpMain;
private System.Windows.Forms.Button btLoad;
private System.Windows.Forms.Button btSave;
private System.Windows.Forms.PropertyGrid pgData;
#endregion
}
}The original DataContainer class
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.Serialization;
namespace Test_Serialization_Versioning_Heavy
{
[Serializable]
public class DataContainer
{
#region Declarations
private string _name = "NoName";
private int _someNumber = 3;
#endregion
#region Information Disclosure
public string Name
{
get { return (_name); }
set { _name = value; }
}
public int SomeNumber
{
get { return (_someNumber); }
set { _someNumber = value; }
}
#endregion
#region Actions
public void Save(string path)
{
using (
System.IO.Stream writeStream = new System.IO.FileStream(
path,
System.IO.FileMode.OpenOrCreate
)
)
{
IFormatter formatter = new Formatters.Soap.SoapFormatter();
formatter.Serialize(writeStream, this);
}
}
public static DataContainer LoadDataContainter(string path)
{
using (System.IO.Stream readStream = new System.IO.FileStream(path, System.IO.FileMode.Open))
{
IFormatter formatter = new Formatters.Soap.SoapFormatter();
return ((DataContainer)(formatter.Deserialize(readStream)));
}
}
#endregion
}
}After updating
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.Serialization;
namespace Test_Serialization_Versioning_Heavy
{
[Serializable]
public class DataContainer
{
#region Declarations
private string _name = "NoName";
private int _someNumber = 3;
private double _newDouble = 5.2;
#endregion
#region Information Disclosure
public string Name
{
get { return (_name); }
set { _name = value; }
}
public int SomeNumber
{
get { return (_someNumber); }
set { _someNumber = value; }
}
public double NewDouble
{
get { return (_newDouble); }
set { _newDouble = value; }
}
#endregion
#region Actions
public void Save(string path)
{
using (
System.IO.Stream writeStream = new System.IO.FileStream(
path,
System.IO.FileMode.OpenOrCreate
)
)
{
IFormatter formatter = new Formatters.Soap.SoapFormatter();
formatter.Serialize(writeStream, this);
}
}
public static DataContainer LoadDataContainter(string path)
{
try
{
using (
System.IO.Stream readStream = new System.IO.FileStream(
path,
System.IO.FileMode.Open
)
)
{
IFormatter formatter = new Formatters.Soap.SoapFormatter();
return ((DataContainer)(formatter.Deserialize(readStream)));
}
}
catch (Exception ex)
{
System.Reflection.Assembly legacyAssembly = System.Reflection.Assembly.Load(Properties.Resources.LegacyAssemblyV1_0_0_0);
Type[] legacyTypes = legacyAssembly.GetTypes();
Type legacyProjectType = legacyAssembly.GetType("Test_Serialization_Versioning_Heavy.DataContainer");
object legacyProjectObject = legacyProjectType.InvokeMember(
"LoadDataContainter",
System.Reflection.BindingFlags.Public
| System.Reflection.BindingFlags.Static
| System.Reflection.BindingFlags.InvokeMethod,
null, null,
new object[] { path }
);
return (null);
}
}
#endregion
}
}
Ciao,
luker
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Generally, that would be the good answer. As I already mentioned
"...at least using ObsoleteAttribute and OptionalFieldAttribute..."
I am aware of the possibilities of Version Tolerant Serialization.
But in this case, I need something more powerful. Hence my approach to load a legacy assembly and make it load the legacy file.
Problem is, the legacy assembly throws an error on loading a file that it should be capable of loading. The error in turn refers to a data type that the legacy assembly cannot know of.
How can I make this work?
Ciao,
luker
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You may need to load the assembly into a separate AppDomain – but that then makes it impossible to copy the object across once it's loaded in the other domain, so it doesn't really help. With my lobby client (which loads its game type modules at runtime and does some version control on them) I had big problems trying to get two version of the same class to operate within one AppDomain.
If the changes are more than just adding new fields, you might want to think about having the class unchanged and creating a new class which inherits from or wraps it. You might also want to look at the design: typically you should be serialising data, i.e. very simple data-containing objects, and I wouldn't expect them to change so much as to make the version tolerance in the framework insufficient.
(The kind of thing you're experiencing here is one reason why I don't like to use [Serializable] for long term persistence, i.e. saving to file or other permanent storage. I typically have read/write methods on the persistent classes which convert them to the string or bytes that are needed to recreate each object – often not the same thing as its complete internal state, which is what serialisation saves – and those methods can handle the reading of prior versions, particularly if you pass as a parameter the version which the file claims to be.)
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hi all,
I am quite new on C# and want to prepare a GUI for an IP device which already has a web page. What I want to do is making my own menu with specific options. For example on web page there are 4 options that i can change/configure but in my GUI i just want to use 2 of them, i want to read these 2 options and want to reconfigure. Any help will welcome!
thx
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i forgot to say that i am working on Microsoft Visual Studio 2010 C# and want to make a form application.
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What's an IP device and what part of the GUI are you struggling with, creating a menu bar?
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For example an IP relay. on its web page i can set the 4 relays on/off and i have config menu. in my gui i just want to play with 2 relays only. basicly it will be a button but how to connect this button click with relay?
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Well the first thing to understand is the protocols used by the IP Relay to control it.
Then you would have to write a suitable communications class to do the interfacing, and on top of that the gui to do the user interaction.
Without more knowledge of the type/make/model of the IP Relay then nothing more can be added. In situations like this, Google and some of the Hardware sites can help. The OEMs usually have samples available on their websites.
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Could you clarify:
1. you are asking for help only in how to make a GUI in a WinForms C# application using some form of menu ?
2. you have already solved all issues relating to how your C# application communicates with your IP device ? So the information you need to display in the C# application is available, and the means to take action ... sending whatever to the IP Device ... depending on the user's choices in the application ... is already worked out ?
3. By 'menu' do you mean the typical drop-down Menu Control ? ... or ... ?
best, Bill
"Beauty is in the eye of the beholder, and it may be necessary from time to time to give a stupid or misinformed beholder a black eye." Miss Piggy"
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That means that you have to analyze the source code of the html pages shown in your web browser.
Find out which actions are invoked on the web server of your device, when a button on the form is clicked (the protocol GET or POST, the address the browser sends the data to, the data which are sent), and then send the equivalent http requests from your application.
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Ex:
If I send user the download url like http://www.mysite.com/downloads/file1.pdf
but there are file2.pdf,file3.pdf in the same folder and user can simple rename the file1.pdf to file2.pdf in the url and he can download file2.pdf.
How can we restrict users from doing this.
I really appreciate for you help....
Thanks
Nani
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How about using randomly generated file names so that the user has no way of replacing the file name?
0100000101101110011001000111001011101001
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You would have to keep the files in a different location and then use a Web Handler file (ASHX) to read the file bytes and Write them to the Response.
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Nani - you actually need to invert your thinking on this. Should you be restricting the user from doing this? If the user has the permissions to download the file then why should you restrict it? If, however, you change the problem around to "should I allow a user to be able to download a file that they don't have permissions to?" then you get a totally different question, but a one that makes a lot of sense.
You can use the security aspects of ASP.NET - and combine this with ashx handlers to parse the request that's coming in - and control the users access to the files. BTW - this should have been asked in the ASP.NET forum, not this one.
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You accomplish this by keeping your assets in a non-accessible location (eg, somewhere in App_Data) and using an HttpHandler to serve the files out after verifying permissions.
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public void RenameSetting(string xPath, string newNode, string oldNode, string bladeName)
{
XmlDocument xmlDocument = new XmlDocument();
string documentPath = Application.StartupPath + "\\groupSettings.xml";
xmlDocument.Load(documentPath);
XmlNode xmlNode = xmlDocument.SelectSingleNode("settings/" + xPath);
XmlNode oldChild = xmlDocument.SelectSingleNode("settings/Groups/" + xmlNode.Name + "/" + oldNode);
XmlNode newChild = xmlDocument.SelectSingleNode("settings/Groups/" + xmlNode.Name + "/" + newNode);
PutSetting("Groups/" + xmlNode.Name + "/" + newNode + "/Name", bladeName);
PutSetting("Groups/" + xmlNode.Name + "/" + newNode + "/User", GetSetting(xPath + "/" + oldNode + "/User", ""));
PutSetting("Groups/" + xmlNode.Name + "/" + newNode + "/Host", GetSetting(xPath + "/" + oldNode + "/Host", ""));
xmlNode.RemoveChild(oldChild);
xmlDocument.Save(documentPath);
}
public void PutSetting(string xPath, string value)
{
XmlNode xmlNode = xmlDocument.SelectSingleNode("settings/" + xPath);
if (xmlNode == null) { xmlNode = createMissingNode("settings/" + xPath); }
xmlNode.InnerText = value;
xmlDocument.Save(documentPath);
}
I call RenameSettings like this:
RenameSetting("Groups/Group2", "Blade5", "Blade4", "Blade 5");
Here is my xmlDocument:
<settings>
<Groups>
<Group2>
<Blade4>
<Name>Blade 4</Name>
<User>k</User>
<Host>7</Host>
</Blade4>
</Group2>
</Groups>
</settings>
In short, I am trying to create a method that can rename my "settings/Groups/Group2/Blade4" to "settings/Groups/Group2/Blade5", my current method should copy everything from Blade4 to Blade5, then delete Blade4, but it throws the error:
the node to be removed is not a child of this node on
xmlNode.RemoveChild(oldChild); and as you can clearly see in the XML, Blade4 (which is oldChild) is most definitely a child of Group2. I assume I am defining oldChild wrong, but how else do you define it so it properly sees oldChild as a child of xmlNode?
modified 22-Sep-11 17:11pm.
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I think your RenameSetting call should be:
RenameSetting("Group2", "Blade5", "Blade4", "Blade 5");
0100000101101110011001000111001011101001
modified 22-Sep-11 17:11pm.
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Actually, wouldn't it be:
RenameSetting("Groups/Group2", "Blade5", "Blade4", "Blade 5");
?
That was just a slight error in my post of so....if you look at my XML though, the full path to Blade4 is: "settings/Groups/Group2/Blade4", if I call RenameSetting like you say I should, then wouldn't every instance of ("settings/" + xPath) resolve to "settings/Group2" which currently doesn't exist in my XML?
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You are right of course.
Did you try debugging the code to see what the value of xmlNode.Name is?
You could also try replacing
XmlNode oldChild = xmlDocument.SelectSingleNode("settings/Groups/" + xmlNode.Name + "/" + oldNode);
with
XmlNode oldChild = xmlDocument.SelectSingleNode("settings/" + xPath + "/" + oldNode);
and see what happens.
0100000101101110011001000111001011101001
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Yes, xmlNode.Name = Group2, exactly what you would expect it to be.
I tried replacing that line with your suggestion, but it didn't change anything....
An interesting thing through, if I break at the "XmlNode newChild" line, and examine "oldChild", it shows the ParentNode as "{Element, Name="Group2"}", which is exactly what you would expect, but then if I break again at "xmlNode.RemoveChild(oldChild);", "oldChild" shows a ParentNode of "null".....so somewhere between line 7 (initialize/define oldChild) and 12 (remove oldChild), oldChild loses its ParentNode attribute......which causes xmlNode to not see oldChild as a child node.
edit: oddly enough, if I examine xmlNode however, oldNode (which is equivilent to "Blade4") IS shown as a child node of xmlNode....yet if I define an XmlNode using my oldNode variable as part of the SelectSingleNode string, xmlNode does NOT see "Blade4" as a valid child node.
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