In MDI application we can have multiple forms and can work with multiple forms i.e. MDI childs at a time but while developing applications we don’t pay attention to the minute details of memory management. Take this as an example, when we develop application say preferably an MDI application, we have multiple child forms inside one parent form. On MDI parent form we would like to have menu strip and tab strip which in turn calls other forms which build the other parts of the application. This also makes our application looks pretty and eye-catching (not much actually). Now on a first go when a user clicks a menu item or a button on a tab strip an application initialize a new instance of a form and shows it to the user inside the MDI parent, if a user again clicks the same button the application creates another new instance for the form and presents it to the user, this will result in the un-necessary usage of the memory. Therefore, if you wish to have your application to prevent generating new instances of the forms then use the below method which will first check if the the form is visible among the list of all the child forms and then compare their types, if the form types matches with the form we are trying to initialize then the form will get activated or we can say it will be bring to front else it will be initialize and set visible to the user in the MDI parent window. The method we are using:

private bool CheckForDuplicateForm(Form newForm)
{
     bool bValue = false;
     foreach (Form frm in this.MdiChildren)
     {
         if (frm.GetType() == newForm.GetType())
         {
             frm.Activate();
             bValue = true;
         }
      }
      return bValue;
}

Usage: First we need to initialize the form using the NEW keyword

ReportForm ReportForm = new ReportForm();

We can now check if there is another form present in the MDI parent. Here, we will use the above method to check the presence of the form and set the result in a bool variable as our function return bool value.

bool frmPresent = CheckForDuplicateForm(Reportfrm);

Once the above check is done then depending on the value received from the method we can set our form.

if (frmPresent)
    return;
else if (!frmPresent)
{
    Reportfrm.MdiParent = this;
    Reportfrm.Show();
}

In the end this is the code you will have at you menu item or tab strip click:

ReportForm Reportfrm = new ReportForm();
bool frmPresent = CheckForDuplicateForm(Reportfrm);
if (frmPresent)
return;
else if (!frmPresent)
{
    Reportfrm.MdiParent = this;
    Reportfrm.Show();
}

Microsoft SQL Server provides the mechanism to save XML data to the SQL table using OpenXML. We can use a stored procedure and pass a XML text as a string. It is useful when we have a large data in XML format and we want to save the whole data in different tables.

So first start declaring the variables. The first declare the document variable and a XML document variable as Varchar(8000) or Varchar(MAX) - It’s a same thing

DECLARE @idoc int
DECLARE @doc varchar(8000)

Now we can set the value to the @doc variable, the @doc variable will accept the XML file as a parameter. We can also have a complete XML data in the parameter only if the XML data is less.

OpenXML takes 3 parameters:

• The handler which we have declare at the begining will holds the XML document in the memory.
• XPath variable to access the various elements of the XML document.
• The last parameter here ‘2’ allows us to access XPath as elements.

Here I have read a XML file in the document variable and store in the table. Here is the full SQL query to achieve this. You can also convert the below code to stored procedure and pass XML file or string as a parameter.

DECLARE @idoc int
DECLARE @doc varchar(8000)
SET @doc ='<ROOT><student>
<id>1</id>
<name>Prashant</name>
<age>32</age>
</student>
<student>
<id>2</id>
<name>Swami</name>
<age>42</age>
</student>
<student>
<id>3</id>
<name>Ash</name>
<age>23</age>
</student>
<student>
<id>4</id>
<name>Kris</name>
<age>12</age>
</student>
<student>
<id>5</id>
<name>Derek</name>
<age>75</age>
</student>
</ROOT>'
 
--Create an internal representation of the XML document.
EXEC sp_xml_preparedocument @idoc OUTPUT, @doc
-- Execute a SELECT statement that uses the OPENXML rowset provider.
Insert into Students SELECT id, name, age from
OPENXML (@idoc, '/ROOT/student',2)
WITH (id  int, name varchar(50), age int)

Microsoft with Jquery team have added the intellisense support for VS2008. I am using Jquery for the past few months, but never thought that it would be great if there would be intellisense support for Jquery. I read Scott Gu’s post of enable intellisense support for Jquery in Visual Studio. The new Visual Studio 2010 comes pre-packed with Jquery intellisense support.

I recently installed Windows 7® Ultimate on my machine and found it more soothing and reliable in terms of preformance than Windows Vista® Ultimate. As a tech enthusiast, I do some serach on the internet and found two links from Microsoft website that will allow developers to develop applications specifically for Windows 7. The Windows API code pack allows developers to develop those features which are not available with .NET Framework. So to get started visit:

• Windows® Code Pack API for Windows 7 & Windows Vista
• Windows Training Kit

The training kit includes the demos and presentations, hand-on labs for developers. I haven’t yet started with Windows 7 development. But as soon as I get started I will blog some demo for Windows 7.

John Grove share a code at MSDN on how can we call DLLs methods dynamically using C# code.

The below code can further be modified and a developer can easily extend the functionality of his application to create a application which accepts DLLs as plug-ins. This concept is useful when different users have different requirements in a generalized application like in the case of famous photo editing program Photoshop from Adobe. Here anyone can create a plug-in and hook it up with the host application which further inherits all the functionalities from the DLL.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Assembly assembly = Assembly.LoadFrom(@"C:\Documents and Settings\john.grove\MyMath.dll");
            Type mathUtility = assembly.GetType("MyMathUtilty");
            Object theInstance = Activator.CreateInstance(mathUtility);
            Int32 result = (Int32)mathUtility.InvokeMember("Add", BindingFlags.InvokeMethod, null, theInstance, new object[] { 56, 26 });
            Console.WriteLine("Dynamically invoking MyMathUtilty Add method");
            Console.WriteLine("56 + 26 = {0}", result);
            Console.WriteLine("");
 
            // get all public static methods of MyMathUtilty type
            MethodInfo[] methodInfos = mathUtility.GetMethods(BindingFlags.Public | BindingFlags.Static);
            Console.WriteLine("All public/static methods in MyMathUtilty");
            Console.WriteLine("----------------------------------------");
            for (Int32 i = 0; i < methodInfos.Count(); i++ )
                Console.WriteLine("{0}.) {1}", i + 1, methodInfos[i].Name);
            Console.ReadLine();
        }
    }
}