I just found this stuff to be very exciting and thought would be worth sharing...

I was reading through the forums and found a particular post.. the description is like this..

The "New" button has to be overridden with a Visualforce Page. When the Visualforce page loads some calculations are performed and the user is either redirected to the standard new/edit page or he stays in the same Visualforce page... And the interesting part was the standard new/edit page has to be prefilled with data passed from the visualforce page...

This is how it can be done.. We will take Account as an example.. We will override the Account new button with a visualforce page..

I will create a Visualforce page.. Just a small one

<apex:page standardController="Account" extensions="newvsold" action="{!pageredir}">

</apex:page>

And the Apex class would be..

public class newvsold
{

public newvsold(ApexPages.StandardController controller)
{

}
public Pagereference pageredir()
{
    Pagereference newpage = new Pagereference ('/001/e?retURL=/001/');
    return newpage;
}
}

So go ahead and override your "new" button with the Visualforce page you just created.. Now when you click on "New" button under Accounts what do you observe..

Yes the same old Account new page is displayed.. It is because we call a method in the "action" attribute of the page tag..(If you are unclear about the "action" attribute then read this article here ).. this method redirects the user to the normal new page.. Now let's analyze the URL we have specified in the Pagerefernce...

/001/e?retURL=/001/ --- The number 001 indicates Account, e indicated edit and retURL specifies where to go after hitting any button on the page.. Like 001 for Account all objects have a number.. You can always check it in the URL bar..

I simply did a redirection.. you can add any complex logic there...

Now going to the interesting part.. How will i prepopulate my new page with values.... Here it is

Go to the Account "new" page...



Right-click and select "View Source" or "View Page Source".... and in the window that appears search for "Account Name"...




Now after the place where you see "Account Name" look for "<input" and note the "id"


In our specific case the id is "acc2" which denotes Account Name....

In the url bar just type ... https://yoursalesforceinstance.com/001/e?acc2=test&retURL=/001/

Or you can modify the Apex Code as below...

public class newvsold
{

   public newvsold(ApexPages.StandardController controller)
   {

   }
   public Pagereference pageredir()
   {
       Pagereference newpage = new Pagereference ('/001/e?acc2=test&retURL=/001/');
       return newpage;
   }  
}

"acc2" denotes Account Name.. similarly all fields have own id... and you can pass values for as many fields as you like unless you do not exceed the maximum URL size...

Even though this sounds a very strange method.. i just thought it might help someone somewhere..

There may be situations in which you would not want a workflow email alert, because either your criteria to send an email may be too complex or the person whom you want to send an email has to be determined dynamically..... In such situations you can choose to send an email from a Apex Class...

Sending an email from a Apex Class is so easy... Basically there are two categories

SingleEmailMessage - This is used when you want to send an email to a single person..

MassEmailMessage - This is used when you want to send an email to a group...

First, let us see about the SingleEmailMessage type....

Step1:

Create a Apex Class with the following code....

public class testemail
{
private final Contact con;
public testemail(ApexPages.StandardController controller)
{
this.con=(Contact)controller.getRecord();
}

public void SendEmail()
{
Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
mail.setTargetObjectId(con.Id);
mail.setTemplateId('00X90000000QHUD');
Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
}
}

Mention a valid Email Template ID in the colored part...

Step 2:

Create a VF page named as "testemail" or anything as your wish , and paste the code below..

<apex:page standardcontroller="Contact" extensions="testemail">
<apex:form>
<apex:commandButton value="Send Email!" action="{!SendEmail}"/>
</apex:form>
</apex:page>

Step 3:

Go to the url bar and type
https://yoursalesforceinstance.com/apx/testemail?id=00390000001TqnV

Note that i have mentioned a valid Contact Id of my organization, make sure you mention a valid contact ID of your SF instance.

Step 4:

You should be able to view the page below



Click on the "Send Email" button and your email is sent to the Email address of the Contact mentioned in the url.....

Analyzing the code.. we can see that four simple lines are enough to send a mail

The first line instantiates an instance of the SingleEmailMessage object...

The second line associates the Contact ID to the email.. this is used to retrieve the toaddress and any merge fields that may be included in your email template...

Note that in the third line we have hardcoded the Email Template ID... This ID belongs to my organization, you will have to replace it with your's...

And in the final step the sendemail method is called and the email is sent...

Template ID

Do you think its weird to hardcode a Template Id in your code.. yes, definitely it is..

There is a EmailTemplate object which you can query and retrieve the template ID you require... below is a small sample which you can plug-in into this example after modifying appropriately..

emailtemplatelist = new List<EmailTemplate>();
for ( EmailTemplate e : [select Id,Name,Subject,body from EmailTemplate where name like :userinputtemplatename+'%'])
{
emailtemplatelist.add(e);
}  

Sending an email without a Template -

The above method is used only when you want to associate a Email Template to your email. When you use an Email Template you will have to specify a valid Contact Id, or User Id, or Lead Id as the target Object Id. If you specify any other object's Id your code wouldn't work.

Overriding a Standard button is pretty straightforward.. but when you override a standard button with a visualforce page all users in your organization would see this page...

So, let's suppose you want one set of users to view a page (for ex: viewpage1) and another set of users to view another page (for ex:viewpage2).

First of all, create the two visualforce pages viewpage1 and viewpage2

Secondly, create a new visualforce page called "viewpageredir". This page would contain the following code...

Note that i have created this page for the "Account" object. I would use this page to override my Account View button. You can use this code for any object by specifying the name of the object in the standardcontroller attribute.

<apex:page showheader="false" action="{!pageredirect}" standardcontroller="Account" extensions="pageredir">

</apex:page>    

The Apex Code would be...

public class pageredir
{

public pageredir(ApexPages.StandardController controller) {

}

public Pagereference pageredirect()
{
if (Userinfo.getUserName() == 'testview1@org.com')
{
Pagereference p = Page.viewpage1;
return p;
} 
else
{
Pagereference p = Page.viewpage2;  
return p;
}  
}      
}    

Now, let's see how this works.. As you can see "viewpageredir" has only one tag "<apex:page>" . There is no other content in this page as we are using it only to redirect the user to his specific page.

We, have an action attribute in the page. The action method is called when the page loads. This causes the method "pageredirect" to be called. In this page we check the current user's Username. "Userinfo" can not only get the username but also the ID, ProfileId etc. See the Apex Language reference for the entire list.

Based on the username, we redirect the user to the desired page......