SPSecurityTrimmedControl is a useful SharePoint control to control the visibility of content and controls on your site. In order to use this control, simply add the following code into your page:

<SharePoint:SPSecurityTrimmedControl runat="server" PermissionsString="ManageLists">
Your code here.
</SharePoint:SPSecurityTrimmedControl>

1. Create a project (It seems .net 4 doesn't work well with SharePoint 2007)
2. Add the reference to Microsoft.Office.Server.dll. (C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\ISAPI)
3. The log code looks like this.

try
{
  throw new Exception("This is a test");
}
catch (Exception ex)
{
  Microsoft.Office.Server.Diagnostics.PortalLog.LogString(ex.Message, null);
}

Done

I find this Post from Dave Wollerman's blog. I think it is very useful to me. Here is the link SharePoint 2007 Single Sign-On Setup

Here is the step you need to do in order to config your SharePoint site using form authentication.

Preparation: You should have a existing ASP.net 2.0 membership database. Here is the link about how to create this database.
There is a existing user testAdmin already created in the membership database.
SQLConnectString in web.config:
<connectionStrings>
<add name="ApplicationServices"  connectionString="Data Source=localhost;User ID=sqluser;Password=Password1;persist security info=False;initial catalog=DemoUser;"  providerName="System.Data.SqlClient" />
</connectionStrings>

Membership Configuration Section in web.config:
<membership>
  <providers>
 <clear/>
 <add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServices"
  enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false"
  maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10"
  applicationName="/" />
  </providers>
</membership>

Step 1. Create a web application and a site collection.

1. Open the SharePoint Central Administration site.
2. Click Application Management tab.
3. Click Create or extend Web application
4. Click Create a new Web Application
5. In the Port textbox, put the port number you want. I am going to use Port 112 in this example.
6. Under "Allow anonymous", Click "Yes".
7. Click Ok.
8. After you get the information says the web application has been successfully create. Click the "Create Site Collection". I am going to create a publishing portal in this example. 
9. Enter the site title. For site template, select the "Publishing Portal" under the Publishing tab.
10. Click Ok.

Step 2. 
1. Open the site we just create. In this example it will be http://localhost:112. 
2. Click the "Enable anonymous access" link in my front page.

3. Click "Entire Web Site".

Step 3. Change the SharePoint authentication method
1. Open the SharePoint Central Administration Site.
2. Click the "Application Management" Tab.
3. Click the "Authentication Providers" under the "Application Security" section.

4. Confirm the web application you want to modify is correct. In this case http://localhost:112
5. Click the Default
6. Change the Authentication Type to "Forms"
7. Set the Membership Provider Name to "AspNetSqlMembershipProvider"
8. Set the Role Manager Name to "AspNetSqlRoleProvider"

9. Click Save.

Step 4 This is step is optional. You only need to do this if you want to set users from your membership database as your site collection administrators.
1. Open the web.config file for your Central Administration. The file is located in "C:\Inetpub\wwwroot\wss\VirtualDirectories\PortNumber" - PortNumber is the port number for your Central Administration site.
2. Add the SQLConnectString and Membership Configuration Section in the web.config.
3. Save and close your web.config file.
4. Open the SharePoint Central Administration Site.
5. Click the "Application Management" Tab.
6. Click "Site Collection Administrators" under the "SharePoint Site Management" Section.
7. Confirm the site collection you want to modify is correct. In this case http://localhost:112
8. For primary site collection administrator type "test" and verify user.  It may take a few seconds, but the page should underline the text in the textbox indicating that the username is valid.
9. Click Ok.

Now if you open the SharePoint site, you should able to see a "Sign In" link at the top of you screen.

Click that link you will able to see your login screen.

Then the screen should look like this. If you configure the step 4, you should be able to see the "Site Actions" menus as well.

How to bulk delete in SharePoint?

The normal way to delete file programmatically in SharePoint is using the SharePoint API. The code looks like:

foreach(SPList myList in myWeb)
{
  foreach( SPListItem item in myList )
  {
    item.Delete();
  }
}

This works fine for document libraries contain small amount of data. It will be extremely slow when you have document libraries contain millions of records. In this case, you will need bulk deletion.

In order to use bulk deletion you need to know the CAML and how to use SPWeb.ProcessBatchData() methods.
There is the example.

private static String BuildBatchDeleteCommand( SPList list, SPListItemCollection coll )
{
  StringBuilder sbDelete = new StringBuilder();
  sbDelete.Append( "<?xml version=\"1.0\" encoding=\"UTF-8\"?><Batch>" );
 
  // We prepare a String.Format with a String.Format, this is why we have a {{0}}
  string command = String.Format( "<Method><SetList Scope=\"Request\">{0}</SetList><SetVar Name=\"ID\">{{0}}</SetVar><SetVar Name=\"Cmd\">Delete</SetVar><SetVar Name=\"owsfileref\">{{1}}</SetVar></Method>", list.ID );
  foreach ( SPListItem item in coll )
  {
    sbDelete.Append( string.Format( command, item.ID.ToString(), item.File.ServerRelativeUrl ) );
  }
  sbDelete.Append( "</Batch>" );
  return sbDelete.ToString();
}

// While there's something left
while ( list.ItemCount > 0 )
{
  // We get everything but we limit the result to 100 rows
  SPQuery q = new SPQuery();
  q.RowLimit = 100;
 
  // We get the results
  SPListItemCollection coll = list.GetItems( q );
 
  // We process a CAML batch
  String batch = BuildBatchDeleteCommand( list, coll );
 
  // We execute it
  web.ProcessBatchData( batch );
 
  list.Update();
}

BTW the methods returns a String, if your code doesn’t work, it would return you an error code. If everything is fine, it just return "0x00000000".

When querying a list in SharePoint, the SPList.GetItems method is a simple and relatively easy way to return a list of records from the SharePoint List (returned as a SPListItemCollection). This is implemented simply as follows:

    using (SPWeb currentWeb = currentSite.OpenWeb(_RelativeWebUrl))
    {
           SPList currentList = currentWeb.Lists[_ListName]; 
           SPListItemCollection items = currentList.GetItems();
    }

As you progress a bit, you will find that you won't necessarily want to return all the items in a list. And the performance is not good when your list has a large amount of items. That's when using the SPQuery object comes in real handy. Simply write the CAML query for the code that you wish to return, then pass the SPQuery object to the GetItems method. This should then return the exact subset of data that you were after. (

    using (SPWeb currentWeb = currentSite.OpenWeb(_RelativeWebUrl))
    {
           SPList currentList = currentWeb.Lists[_ListName];
           SPQuery query = new SPQuery();                   
           query.Query = String.Format("<Where><Eq><FieldRef Name=\"{0}\" /><Value Type=\"{1}\">{2}</Value></Eq></Where>",_InternalName, _Type,_Value);    
           SPListItemCollection items = currentList.GetItems(query);
    }

HOWEVER, you must be careful that you write your CAML code correctly, or the method will return all records! This really surprised me and is a strange 'feature' one would think - I personally would have thought this should have returned NO records if it the query was incorrect. So basically if you find that every time you run a query there is a full record set returning, then check your CAML query...

U2U CAML Query Builder - It is a wonderful tool to test your CAML query.