C# : Database monitoring system using XML file

This application monitors the database of any kinds like employee, patients, or any items via XML. The XML file has a very nice interface to store the data, retrieve and update with O(1) time and hence it will be much faster as all the nodes will be unique. The search operation also use Hashing mechanism on XML node. This is very useful interface for any kind of application.

Where I have used below windows components:

private Button button3;

You can get the InitializeComponent routine from here http://www.eggheadcafe.com/fileupload/-698781408_intialize_components.zip so that it will generate the similar form that I have given above. The XML file that I have used in the project available at
http://www.eggheadcafe.com/fileupload/-698781408_company.zip

The output of application:



You can see that I have searched for Empid 101 and result have been displayed.

You can modify the XML file loaded into the text box and save it.

Rest of my code is below: You can copy paste it below the Initialization function:

        [STAThread]
        static void Main() 
        {
            Application.Run(new EmployeeDatabase());
        }






 
        //Load the XML file into Text box on Form loading event
        private void Form1_Load(object sender, EventArgs e)
        {
            if (e == null) throw new ArgumentNullException("e");
            try
            {
                DataSet ds = new DataSet();
                ds.ReadXml(@"..\..\company.xml");
                dataGrid1.DataSource = ds.Tables[0]; 
                XmlDataDocument xd = new XmlDataDocument(ds);              
                if (xd.InnerXml != null) TextBox1.Text = xd.InnerXml;
            }
            catch (XmlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

 
        //Save the modified XML file when user sclicks Save button
        private void button2_Click(object sender, EventArgs e)
        {
            if (e == null) throw new ArgumentNullException("e");
            try
            {
                XmlTextReader xr = new XmlTextReader(
                    new StringReader(TextBox1.Text));
                DataSet ds = new DataSet();
                ds.ReadXml(xr);
                XmlDataDocument xd = new XmlDataDocument(ds);
                ds.WriteXml(@"..\..\company.xml");
                dataGrid1.DataSource = xd.DataSet.Tables[0];
            }
            catch (XmlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }


 
        //Allow only one radio button to be selected for searching based on Emp_ID
        //or Emp_Name
        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {
            if (e == null) throw new ArgumentNullException("e");
            TextBox2.ReadOnly = false;
            TextBox3.ReadOnly = true;
            TextBox2.Focus();
        }

        private void radioButton2_CheckedChanged(object sender, EventArgs e)
        {
            if (e == null) throw new ArgumentNullException("e");
            TextBox2.ReadOnly = true;
            TextBox3.ReadOnly = false;
            TextBox3.Focus();
        }

        // When user select any of radio button and clicks search button then search the
        //XML file for required data and display 
        private void button1_Click(object sender, EventArgs e)
        {
            DataSet ds = new DataSet();
            ds.ReadXml(@"..\..\company.xml");
            dataGrid1.DataSource = ds.Tables[0];
            XmlDataDocument xd = new XmlDataDocument(ds);
            
            if(button1.Text.Equals("Search"))
            {
                if (radioButton1.Checked)
                {
                    XPathNavigator xn = xd.CreateNavigator();
                    XPathExpression expr = null;
                    try
                    {
                        if (xn != null)
                            expr = xn.Compile(
                                "descendant::employees[id="+
                                TextBox2.Text + "]");
                        if (xn != null)
                        {
                            XPathNodeIterator iterator = xn.Select(expr);
                            if(xn.Select(expr).Count == 0)
                            {
                                MessageBox.Show("Enter a valid employee Id number");
                                TextBox2.Text ="";
                                TextBox3.Text ="";
                                TextBox4.Text="";
                                button1.Text ="Search";
                                groupBox1.Text = "Enter Search";
                                TextBox2.Focus();
                                return;
                            }
                            iterator.MoveNext();
                            XPathNavigator nav2 = iterator.Current.Clone();
                            nav2.MoveToFirstChild();
                            TextBox2.Text = nav2.Value;
                            nav2.MoveToNext();
                            TextBox3.Text = nav2.Value;
                            nav2.MoveToNext();
                            TextBox4.Text = nav2.Value;
                        }
                    }                    
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.Message);
                    }
                }
                else if (radioButton2.Checked)
                {
                    XPathNavigator xn = xd.CreateNavigator();
                    XPathExpression expr = null;
                    try
                    {
                        if (xn != null)
                            expr = xn.Compile(
                                "descendant::employees[name='" +
                                TextBox3.Text + "']");
                        XPathNodeIterator iterator = null;
                        if (xn != null)
                        {
                            iterator = xn.Select(expr);
                            if(xn.Select(expr).Count == 0)
                            {
                                MessageBox.Show("Enter a valid employee name(case sensitive).");
                                TextBox2.Text ="";
                                TextBox3.Text ="";
                                TextBox4.Text="";
                                button1.Text ="Search";
                                groupBox1.Text = "Searching String:";
                                TextBox3.Focus();
                                return;
                            }
                        }
                        if (iterator != null)
                        {
                            iterator.MoveNext();
                            XPathNavigator nav2 = iterator.Current.Clone();
                            nav2.MoveToFirstChild();
                            TextBox2.Text = nav2.Value;
                            nav2.MoveToNext();
                            TextBox3.Text = nav2.Value;
                            nav2.MoveToNext();
                            TextBox4.Text = nav2.Value;
                        }

                    }
                    catch (XPathException exp)
                    {
                        MessageBox.Show(exp.Message);
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.Message);
                    }
                }    
                button1.Text = "Complete";
                groupBox1.Text = "Done";
            }        
            else
            {
                TextBox2.Text ="";
                TextBox3.Text ="";
                TextBox4.Text="";
                button1.Text ="Search";
                groupBox1.Text = "Search String:";
            }
        }


        
        //When user modifies the textbos XML content then synchronize the changed XML in
        //DataGrid
        private void dataGrid1_CurrentCellChanged(object sender, EventArgs e)
        {
            if (e == null) throw new ArgumentNullException("e");
            //This function syncronize the data in datagrid and XML
            DataSet ds = new DataSet();
            ds.ReadXml(@"..\..\company.xml");
            dataGrid1.DataSource = ds.Tables[0];
            XmlDataDocument xd = new XmlDataDocument(ds);
            TextBox1.Text = xd.InnerXml;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }
    }