.NET  C#

Saving and Opening a File

If we wish to save the file we can click on 'Save' menu item. When we do so, save_Click( ) handler gets called. The handler is shown below:

private void save_Click(object sender, EventArgs e)
{
    SaveFileDialog sd = new SaveFileDialog();
    sd.Filter = "dat files ( *.dat ) | *.dat";  
    if (sd.ShowDialog() == DialogResult.OK)
    {
        FileInfo f = new FileInfo(sd.FileName);
        Stream st = f.Open(FileMode.Create, FileAccess.ReadWrite);
        foreach (shapes t in s)
            b.Serialize(st, t);
        st.Close();
    }
}

Here we have created an object of the SaveFileDialog class and used a "*.dat" filter for it. When we type in a file name and click OK, a FileInfo object gets created with the selected filename. The Open( ) function returns a Stream object associated with the file. We have collected it in a Stream reference. Then we have used a BinaryFormatter object to serialize the objects. This binary formatter is added as a data member of the form class as shown below:

BinaryFormatter b = new BinaryFormatter();

BinaryFormatter serializes and deserializes an object, in binary format. The Serialize( ) method of this class serializes the object to the given stream. After serializing all the elements of the array, we have closed the stream using the Close( ) method.

When we click 'Open' menu, the open_Click( ) event handler gets called. This handler is given below:

private void open_Click(object sender, EventArgs e)
{
           OpenFileDialog od = new OpenFileDialog();
           od.Filter = "dat files ( *.dat )|*.dat";
           if (od.ShowDialog() == DialogResult.OK)
            {
                FileInfo f = new FileInfo(od.FileName);
                Stream st = f.Open(FileMode.Open);
                while (st.Position != st.Length)
                    s.Add(b.Deserialize(st));
                st.Close();
            }
            Invalidate();
 }

Here firstly we have created an object of the OpenFileDialog class and displayed the dialog using the ShowDialog( ) method. In this method too we have created a FileInfo object and collected the corresponding Stream object of the specified file. Next we have used a while loop to deserialize the objects until the end of stream is reached. The Deserialize( ) method deserializes the specified stream into an object. We have collected these objects into our array by using the Add( ) method, closed the stream and called Invalidate( ) function for painting these shapes.

When we click 'New' menu item the following handler gets called:

 private void filenew_Click(object sender, EventArgs e)
{
     s.Clear();
     Invalidate();
}

Here we have cleared the array list by deleting all the elements in it using the Clear( ) method. After this we have called Invalidate( ). This time the method Form1_Paint( ) draws nothing as the array is empty, thereby resulting in a clean form.

On clicking the 'Exit' menu item the Dispose( ) method gets called and the form is disposed.

private void exit_Click(object sender, EventArgs e)
{
     Dispose();
}