Server.Transfer Vs. Response.Redirect

Website:

The Web Site project is compiled on the fly. You end up with a lot more DLL files, which can be a pain. It also gives problems when you have pages or controls in one directory that need to reference pages and controls in another directory since the other directory may not be compiled into the code yet. Another problem can be in publishing.

If Visual Studio isn't told to re-use the same names constantly, it will come up with new names for the DLL files generated by pages all the time. That can lead to having several close copies of DLL files containing the same class name, which will generate plenty of errors. The Web Site project was introduced with Visual Studio 2005, but it has turned out not to be popular.

Web Application:

The Web Application Project was created as an add-in and now exists as part of SP 1 for Visual Studio 2005. The main differences are the Web Application Project was designed to work similarly to the Web projects that shipped with Visual Studio 2003. It will compile the application into a single DLL file at build time. To update the project, it must be recompiled and the DLL file published for changes to occur.

Another nice feature of the Web Application project is it's much easier to exclude files from the project view. In the Web Site project, each file that you exclude is renamed with an excluded keyword in the filename. In the Web Application Project, the project just keeps track of which files to include/exclude from the project view without renaming them, making things much tidier.

Reference

The article ASP.NET 2.0 - Web Site vs Web Application project also gives reasons on why to use one and not the other. Here is an excerpt of it:

• You need to migrate large Visual Studio .NET 2003 applications to VS 2005? use the Web Application project.
• You want to open and edit any directory as a Web project without creating a project file? use Web Site project.
• You need to add pre-build and post-build steps during compilation? use Web Application project.
• You need to build a Web application using multiple Web projects? use the Web Application project.
• You want to generate one assembly for each page? use the Web Site project.
• You prefer dynamic compilation and working on pages without building entire site on each page view? use Web Site project.
• You prefer single-page code model to code-behind model? use Web Site project.

Web Application Projects versus Web Site Projects (MSDN) explains the differences between the web site and web application projects. Also, it discusses the configuration to be made in Visual Studio.

Access modifiers

From docs.microsoft.com:

public

The type or member can be accessed by any other code in the same assembly or another assembly that references it.

private

The type or member can only be accessed by code in the same class or struct.

protected

The type or member can only be accessed by code in the same class or struct, or in a derived class.

private protected (added in C# 7.2)

The type or member can only be accessed by code in the same class or struct, or in a derived class from the same assembly, but not from another assembly.

internal

The type or member can be accessed by any code in the same assembly, but not from another assembly.

protected internal

The type or member can be accessed by any code in the same assembly, or by any derived class in another assembly.

When no access modifier is set, a default access modifier is used. So there is always some form of access modifier even if it's not set.

static modifier

The static modifier on a class means that the class cannot be instantiated, and that all of its members are static. A static member has one version regardless of how many instances of its enclosing type are created.

A static class is basically the same as a non-static class, but there is one difference: a static class cannot be externally instantiated. In other words, you cannot use the new keyword to create a variable of the class type. Because there is no instance variable, you access the members of a static class by using the class name itself.

However, there is a such thing as a static constructor. Any class can have one of these, including static classes. They cannot be called directly & cannot have parameters (other than any type parameters on the class itself). A static constructor is called automatically to initialize the class before the first instance is created or any static members are referenced. Looks like this:

static class Foo()
{
    static Foo()
    {
        Bar = "fubar";
    }
    
    public static string Bar { get; set; }
}

Static classes are often used as services, you can use them like so:

MyStaticClass.ServiceMethod(...);