Confessions of a .NET Developer!

Saving forms settings(location, height) using Serialization

In some applications, there might be some requirements
where you have to load last used form settings like Location, Height and Width the next time you open the form. Well you can create an XML Document with attributes like Location, Width and Height and save it at some location. And then use the XMLDocument class to load and traverse the XML to retrieve the settings. I will bring another, easy way; by using Serialization.

I won’t be going to the details of what Serialization or Deserialization is, as it can be found in many introductory C# books and online tutorials. The only purpose here is to show how can I put Serialization to use.

Basically there are three types of Serialization:
1) BinaryFormatter
2) SoapFormatter
3) XMLFormatter

I will be using Soap as this is the preferred way to persist the object state to be used by any operating system or any framework. XMLFormatter is also a choice but it cannot serialize private fields.

Alright let’s get started.

First create a Windows Forms application and add the following labels as shown in the window.

Labels

Labels

These labels will show the location, height and width of the form to be crossed checked later when we next time open the form.

Next we will create a class named FormSettings whose object we want to persist. As we are using Serialization, this class will be a serialized class by specifying the [Serializable] attribute on top of the class declaration.
The class will look like this:

    [Serializable]
    class FormSettings
    {
        public Point FormLocation { get; set; }
        public FormWindowState WindowState{ get; set; }
        public int Height { get; set; }
        public int Width { get; set; }

        public FormSettings(Point _formLoc, FormWindowState _windowState, int _height, int _width)
        {
            FormLocation = _formLoc;
            WindowState = _windowState;
            Height = _height;
            Width = _width;
        }
    }

Lets get back to the code-behind of our form.
We will declare two private string fields, dirPath and filePath and and four event handlers as shown below.

    public partial class Form1 : Form
    {
        string dirPath = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData) +
            @"\FormSettings\";

        string filePath;

        public Form1()
        {
            InitializeComponent();

            this.Load += new EventHandler(Form1_Load);
            this.FormClosed += new FormClosedEventHandler(Form1_FormClosed);
            this.Move += new EventHandler(Form1_Move);
            this.Resize += new EventHandler(Form1_Resize);
        }

dirPath is the folder where we will keep the file which in turn will store FormSettings class’s object’s data.

Let’s first discuss the Move and Resize event:

        void Form1_Move(object sender, EventArgs e)
        {
            lblX.Text = this.Location.X.ToString();
            lblY.Text = this.Location.Y.ToString();
        }

        void Form1_Resize(object sender, EventArgs e)
        {
            lblHeight.Text = this.Height.ToString();
            lblWidth.Text = this.Width.ToString();
        }

Whenever our form is moved or resized, the labels will update the current location and width and height accordingly.

Now let us discuss the Load event.

        void Form1_Load(object sender, EventArgs e)
        {
            LoadSettings();
        }

        private void LoadSettings()
        {
            if (!Directory.Exists(dirPath))
            {
                Directory.CreateDirectory(dirPath);
            }

            filePath = dirPath + @"\Settings.dat";

            if (File.Exists(filePath))
            {
                using (FileStream stream = new FileStream(filePath, FileMode.Open,
                    FileAccess.Read, FileShare.None))
                {
                    SoapFormatter sf = new SoapFormatter();
                    FormSettings settings = (FormSettings)sf.Deserialize(stream);

                    this.Location = settings.FormLocation;

                    if (settings.WindowState == FormWindowState.Maximized)
                    {
                        this.WindowState = FormWindowState.Maximized;
                    }
                    else
                    {
                        this.Width = settings.Width;
                        this.Height = settings.Height;
                    }
                }
            }
        }

Seems to be quite big but its simple.

Scenario 1: When the form is loaded for the very first time.

When the form is loaded for the very first time, it will create a Folder named FormSettings in CommonApplicationData(where all the users can share) directory. And the Settings.dat is appended to the dirPath creating a filePath string. But wait, as it is loaded for the very first time, we don’t have any previous data of location, width or height, hence no need to create the Settings.dat file.

We will create this file in the Closed event as shown below.

Next let us discuss the Closed event.

        void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            SaveSettings();   
        }

        private void SaveSettings()
        {
            FormSettings settings = new FormSettings(this.Location, this.WindowState, 
                this.Height, this.Width);

            using (FileStream stream = new FileStream(filePath, FileMode.Create, 
                FileAccess.ReadWrite, FileShare.None))
            {
                SoapFormatter sf = new SoapFormatter();
                sf.Serialize(stream, settings);
            }
        }

After moving and adjusting the height(to lets say 300), width(250) and location(50,50) (remember that we are considering scenario 1), let’s close the form. Before closing it, we need to save the location(50,50) and other settings to Settings.dat. But as we don’t have the file created, we will create it now by giving FileMode.Create enum which will create if the file doesn’t exist. Now that our file has been created, we will create an instance of SoapFormatter class and use the Serialize method to save the object in that file.
So what happened in our first scenario is that, the file got created and last used location(50,50), height(300) and width(250) got saved as FormSettings object in that file.
Below is the image showing the form position at (50,50).

Scenario1

Scenario1

Scenario2: Opening the form for the nth time.
Let’s again open the form. So the Load event will be called which in turn will call the LoadSettings function.
Let’s again have a look at it:

        private void LoadSettings()
        {
            if (!Directory.Exists(dirPath))
            {
                Directory.CreateDirectory(dirPath);
            }

            filePath = dirPath + @"\Settings.dat";

            if (File.Exists(filePath))
            {
                using (FileStream stream = new FileStream(filePath, FileMode.Open,
                    FileAccess.Read, FileShare.None))
                {
                    SoapFormatter sf = new SoapFormatter();
                    FormSettings settings = (FormSettings)sf.Deserialize(stream);

                    this.Location = settings.FormLocation;

                    if (settings.WindowState == FormWindowState.Maximized)
                    {
                        this.WindowState = FormWindowState.Maximized;
                    }
                    else
                    {
                        this.Width = settings.Width;
                        this.Height = settings.Height;
                    }
                }
            }
        }

When the program execution reaches this function, first it will check whether our directory exists. Yes it does exist when we first run the form before. Then it checks whether the file exists. Again yes it does exist, we created it when we first run the form and created on the Close event.
So now it enters the if(FileExists…) condition. We open the file using FileStream, create the SoapFormatter object and “deserialize” the FormSettings object from the stream. The deserialize method returns an object, hence we have to cast it to FormSettings, lets say the name of the FormSettings object is settings. Retrieve the FormLocation(50,50), width(250) and height(300) of the form from the settings object and set the form’s location, width and height accordingly. So now we got the last used the Width, Height and Location of the form. Excellent.
Below is the snapshot showing the form at (50,50) which was the location that was opened last time.

Scenario2(AfterOpening)

Scenario2 (After Opening)

Now play around with the form, change the location to (100,100) , width to 400, location to 500 and then close it. Now when we close it, SaveSettings function will be called, we need to store the settings that we changed just now back to the file.
Lets have a look at the SaveSettings function now:

        private void SaveSettings()
        {
            FormSettings settings = new FormSettings(this.Location, this.WindowState, 
                this.Height, this.Width);

            using (FileStream stream = new FileStream(filePath, FileMode.Create, 
                FileAccess.ReadWrite, FileShare.None))
            {
                SoapFormatter sf = new SoapFormatter();
                sf.Serialize(stream, settings);
            }
        }

Just to remind ourselves, we now need to store the location(remember 100,100?) and other settings which we just changed back to the file so that the next time the form is opened, the location of the form should be at (100,100).
The interesting thing is that, FileMode.Create won’t actually create another file, as our file already exists, it will instead overwrite the already present data and that is what we wanted! to store the new location(100,100).
So the serialize method will store the settings into the file. So when AGAIN when you open the form, the form will be set at 100,100.

Oh almost forgot, also check out the WindowState property. If it is maximized, then we don’t need the height and width of the form. Hence the next time the window opens, it will be in the maximized state only.

Phew! That’s it! Have fun playing around with it.
Do let me know if there is any kind of bugs that you found.
Cheers!

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July 5, 2011 Posted by | C Sharp, Winforms | 1 Comment

How to dynamically load assemblies including unreferenced assemblies

This post will explain how to load the dll dynamically and use the class’s methods in that dll. We will use the Activator class to create an instance of a class from the dll and invoke the required methods. So lets get started.

First of all, create a base class library and name it as AClassLibrary:

ClassLibrary

ClassLibrary

Add a new class named AClass, it will look like this:

    public class AClass
    {
        public void WriteDefault()
        {
            Console.WriteLine("A text");
        }

        public void WriteIt(string text)
        {
            Console.WriteLine(text);
        }

        public void WriteIt(string text1, string text2)
        {
            Console.WriteLine(text1 + text2);
        }
    }

Do note that we have two overloaded functions named WriteIt, I will let you know its significance later.

Now lets create another Console Application project in the same solution named CaptureAssembly.
After that, Add Reference to the project AClassLibrary:

AddReference

AddReference

Before explaining, let me show you the whole code:

using System;
using System.Reflection;

namespace CaptureAssembly
{
    class Program
    {
        static void Main(string[] args)
        {
            Assembly a = Assembly.LoadFrom("AClassLibrary.dll");

            Type clsType = a.GetType("AClassLibrary.AClass");
            
            //Create the instance of the class
            object clsInstance = Activator.CreateInstance(clsType, null);

            //Calls the WriteDefault method of AClass
            clsType.InvokeMember("WriteDefault", BindingFlags.InvokeMethod, null, clsInstance, null);

            //Calls the WriteIt methods
            clsType.InvokeMember("WriteIt", BindingFlags.InvokeMethod, null, clsInstance, new object[] { "Hello", " Tarun Kumar" });
            clsType.InvokeMember("WriteIt", BindingFlags.InvokeMethod, null, clsInstance, new object[] { "Hello" });

            Console.ReadLine();
        }
    }
}

First we get the type of AClass using the Reflection. The Activator class will use it to create the instance of the class which we name it as clsInstance.
Next step is to call the 3 methods of AClass. We will use the InvokeMember property using clsType. Let’s take the case of the fist InvokeMethod. The first parameter will take the name of the method, second will help us streamline the search for the method as Reflection is used for this purpose. Third parameter is of no use for now. Fourth parameter, the target is the class instance named clsIntance and the last parameter will take the array of objects used to pass the parameters for the method, as WriteDefault doesn’t have any parameters, hence it will remain null.
The next two invoke methods is for the two overloaded methods WriteIt, the first one will call the method which has two parameters as we are passing two items in the object array(last parameter). As the second invoke method has one item in the object array, hence WriteIt(string text) will be called.

And here is the result:

Result

Result

For loading Unreferenced Assemblies

You can also load the assembly without adding any reference. Suppose the base class library(dll) is in some location, then we can use Assembly.LoadFile method to load the assembly.

Just replace

Assembly a = Assembly.LoadFrom("AClassLibrary.dll");

with

Assembly a = Assembly.LoadFile(@"C:\AClassLibrary\bin\Debug\AClassLibrary.dll");

and you will get the same result.

Happy coding!

June 30, 2011 Posted by | C Sharp, Winforms, WPF | 1 Comment

Allow numbers or letters and disable right-click in textbox

I have seen a number of people asking how to allow only numbers to be added in to a textbox, sometimes only letters etc. Also to disable right-click to disable pasting. One such question can be found here: http://www.codeproject.com/Answers/208641/Wish-to-use-text-box-to-only-allow-numeric-Data-en/?cmt=114369#answer4 to which my friend Chanakya(a pro-photographer with excellent technical skills) gave an excellent, sweet and simple answer, also do read the comments. I got inspiration from him to write this post.
So I will create a new TextBox which will handle all the above things. Its a “derived” control where I create a class which derives from TextBox class.

Here is the class:

    class NewTextBox : System.Windows.Forms.TextBox
    {
        private ContextMenu OrgContextMenu;
        private RestrictType _restrictOptions = RestrictType.None;
        public RestrictType RestrictOptions
        {
            get { return _restrictOptions; }
            set { _restrictOptions = value; }
        }

        private bool _allowPaste = true;
        private ContextMenu PrevContextMenu { get; set; }
        private bool _setOnceFlag = false;

        public bool AllowPaste
        {
            get { return _allowPaste; }
            set
            {
                _allowPaste = value;
                DisableRightClick(value);
            }
        }

        protected override void OnKeyDown(KeyEventArgs e)
        {
            //To only allow numbers 
            if (RestrictOptions == RestrictType.OnlyNumbers)
            {
                if (char.IsNumber((char)e.KeyValue) || (((char)e.KeyData) == '\b'))
                {
                    e.SuppressKeyPress = false;
                }
                else { e.SuppressKeyPress = true; }
            }

            // To only allow letters
            else if (RestrictOptions == RestrictType.OnlyLetters)
            {
                if (char.IsLetter((char)e.KeyValue) || (((char)e.KeyData) == '\b'))
                {
                    e.SuppressKeyPress = false;
                }
                else { e.SuppressKeyPress = true; }
            }

            //To only allow 0's and 1's
            else if (RestrictOptions == RestrictType.OnlyBinary)
            {
                if (((char)e.KeyValue).Equals('1') || ((char)e.KeyValue).Equals('0')
                    || (((char)e.KeyData) == '\b'))
                {
                    e.SuppressKeyPress = false;
                }
                else { e.SuppressKeyPress = true; }
            }
        }

        //To disable Cntl + V for pasting
        protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
        {
            if (AllowPaste.Equals(false))
            {
                if (keyData == (Keys.Control | Keys.V))
                {
                    return true;
                }
                else { return false; }
            }
            else { return false; }
        }

        // Disable Right-click for pasting
        private void DisableRightClick(bool enable)
        {
            if (_setOnceFlag == false)
            {
                OrgContextMenu = this.ContextMenu;
                _setOnceFlag = true;
            }
            if (enable.Equals(false))
            {
                // This will create a new ContextMenu with no options, hence no dropdown will be visible.
                this.ContextMenu = new ContextMenu();
            }
            // Set the original context menu.
            else
            { this.ContextMenu = OrgContextMenu; }
        }
    }

And an enum called RestrictType:

    public enum RestrictType
    {
        OnlyNumbers,
        OnlyLetters,
        OnlyBinary,
        None
    }

The code is self-explanatory. To briefly explain, I have created three properties, one is RestrictOptions which is of type RestrictType to let the user choose he/she wants allow numbers or letters or binary. Then the second property is to whether to disable pasting or not. The ProcessCmdKey function will take care of Ctrl + V, disabling it whenever the combination is used, and then using DiableRightClick function to disable Right-click by showing an empty ContextMenu. These two will be set by the user and by default, AllowPaste is true and RestrictType is None. The other property which is private is OrgContextMenu which will store the initial and original ContextMenu of the Textbox which will be set only one time.

Time to use it:

        public Form1()
        {
            InitializeComponent();
            newTextBox1.RestrictOptions = RestrictType.OnlyNumbers;
            newTextBox1.AllowPaste = false;
        }

Please do give your comments and valuable suggestions for improvement. 🙂
Happy Coding!

June 26, 2011 Posted by | C Sharp, Winforms | 1 Comment

How to use Owner Drawn Controls

There are few controls which support Owner-drawing such as ListBox, ListView,
TreeView, Combobox to name a few. With owner-drawing, you can manipulate the individual items in the above mentioned controls. Each item can be painted using the Graphics object.

In our example, we will use a Listbox having a list of all names of Brushes. Then we will supply the BackColor of each item based on the item’s text(name of Brush).
First step is to set the DrawMode property which takes the DrawMode enum as value. It has three options:
1)Normal – Drawn by operating system, not in our control.
2)OwnerDrawFixed – To be drawn by using our logic with the condition that all the items will be having the same height and width.
3)OwnerDrawVariable – Same as OwnerDrawFixed except that we have to supply the logic for height and width.

Normal won’t be of use in this example as we are going to apply our own logic for drawing of items.
Lets consider using OwnerDrawFixed.
Now to draw the items, we would have to use DrawItem event of ListBox.

Before that, first let us load all the names of the Brushes in the ListBox.

        void Form1_Load(object sender, EventArgs e)
        {
            foreach (PropertyInfo info in typeof(Brushes).GetProperties())
            {
                listBox1.Items.Add(info.Name);
            }
        }

We are using Reflection here to get all the properties and adding each property’s name in to the ListBox.

This is how the window will look like:

SimpleView

SimpleView

Our next task is to give a Background Color for each item in the ListBox depending on the item’s text. For that we will set the DrawMode of ListBox1.

listBox1.DrawMode = DrawMode.OwnerDrawFixed;

Next use the DrawItem event.

listBox1.DrawItem += new DrawItemEventHandler(listBox1_DrawItem);

And the method definition:

void listBox1_DrawItem(object sender, DrawItemEventArgs e)
{
    Brush brush;
    // Take the text from the current listbox item
    string text = listBox1.Items[e.Index].ToString();
    brush = new SolidBrush(Color.FromName(text));
    // Fill the background
    e.Graphics.FillRectangle(brush, e.Bounds);
    // Display the text using the default font and with black foreground
    e.Graphics.DrawString(text, e.Font, Brushes.Black, e.Bounds.X, e.Bounds.Y);
}

And our window will look like this:

OwnerDrawFixed

OwnerDrawFixed

But one small issue is the spacing, the items are closely spaced. Lets provide more spacing by increasing the height of each item. For that we have to set the DrawMode property to OwnerDrawVariable.

listBox1.DrawMode = DrawMode.OwnerDrawVariable;

Our DrawItem event will remain the same but we have to use an additional event “MeasureItem” to alter the height.

listBox1.MeasureItem += new MeasureItemEventHandler(listBox1_MeasureItem);

And the method definition:

void listBox1_MeasureItem(object sender, MeasureItemEventArgs e)
{
   e.ItemHeight = 20;            
}

So now our final window will look like this:

OwnerDrawVariable

OwnerDrawVariable

This is the final source code:

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.Load += new EventHandler(Form1_Load);
            //listBox1.DrawMode = DrawMode.OwnerDrawFixed;
            listBox1.DrawMode = DrawMode.OwnerDrawVariable;
            listBox1.DrawItem += new DrawItemEventHandler(listBox1_DrawItem);
            listBox1.MeasureItem += new MeasureItemEventHandler(listBox1_MeasureItem);
        }

        void listBox1_MeasureItem(object sender, MeasureItemEventArgs e)
        {
            e.ItemHeight = 20;            
        }

        void listBox1_DrawItem(object sender, DrawItemEventArgs e)
        {
            Brush brush;
            string text = listBox1.Items[e.Index].ToString();
            brush = new SolidBrush(Color.FromName(text));
            e.Graphics.FillRectangle(brush, e.Bounds);

            e.Graphics.DrawString(text, e.Font, Brushes.Black, e.Bounds.X, e.Bounds.Y);
        }

        void Form1_Load(object sender, EventArgs e)
        {
            foreach (PropertyInfo info in typeof(Brushes).GetProperties())
            {
                listBox1.Items.Add(info.Name);
            }
        }
    }

June 26, 2011 Posted by | Winforms | Leave a comment