Lesson 12	Course Project Interactive Message
Objective	Put an interactive message into the course project.

ASP Course Project - Interactive Message

The last few lessons have provided you a number of programming techniques that can put interactivity into an HTML Web page by inserting one or more lines of ASP.net code.

To use Blazor on ASP.NET for data manipulation and logic-based processing (constants, variables, totals, branching, loops, and type checks), you rely on C# code within Blazor components. Below is a breakdown of how to accomplish each of the five objectives in Blazor using best practices.

Create and Store Constant or Variable Data
- Blazor uses C# for logic. You define variables and constants inside @code { } blocks of Razor (.razor) components.
- Example:
```
@page "/data"
```
  Constant and Variable Demo
  
  Sales Tax Rate: @TaxRate
  
  Product Name: @productName
```
@code {
    private const decimal TaxRate = 0.07M; // constant
    private string productName = "Gaming Keyboard"; // variable
    private int quantity = 2;
    private decimal price = 59.99M;
}
```

Calculate Totals and Percentages

Use C# arithmetic operations and format them in Razor:

Subtotal: @(price * quantity):C
Tax: @((price * quantity) * TaxRate):C
Total: @((price * quantity) * (1 + TaxRate)):C

Or encapsulate logic in a method:

Total: @CalculateTotal():C

@code {
    private decimal CalculateTotal()
    {
        decimal subtotal = price * quantity;
        return subtotal + (subtotal * TaxRate);
    }
}

Branch and Loop

Branching:

@if (quantity > 5)
{
    Bulk discount applies.
}
else
{
    No discount.
}

Looping:


@foreach (var item in shoppingCart)
{
    @item
}


@code {
    private List<string> shoppingCart = new() { "Mouse", "Keyboard", "Monitor" };
}

Test Data Types and Values

Use is, typeof, or nullable checks:

@code {
    private object data = "Hello Blazor";

    private string TypeCheck()
    {
        if (data is string)
            return "It's a string!";
        else if (data is int)
            return "It's an integer.";
        return "Unknown type.";
    }
}
@TypeCheck()

Value comparison:

@if (price == 59.99M)
{
    Price is set correctly.
}

Manipulate Numeric, Character, and Date Data

Built-in Methods:

@code {
    private DateTime today = DateTime.Now;
    private string upperName = "blazor".ToUpper();
    private double sqrtValue = Math.Sqrt(25);
}
Today: @today.ToShortDateString()
Name Uppercase: @upperName
Square Root of 25: @sqrtValue

User-defined function:

@code {
    private string FormatProduct(string name, decimal price)
    {
        return $"{name} - {price:C}";
    }
}
@FormatProduct("Webcam", 79.99M)

✅ Summary Table

Task	Syntax Example
Constant	`private const int MaxQty = 10;`
Variable	`private string name = "Blazor";`
Total Calculation	`subtotal = qty * price;`
Branching (`if`, `else`)	`if (qty > 5) { ... }`
Looping (`foreach`, `for`)	`foreach (var item in list) { ... }`
Type Checking	`if (obj is string)`
Built-in Functions	`DateTime.Now`, `Math.Sqrt(x)`, `string.ToUpper()`
User-defined Function	`private string Format(...) { return ... }`

Don't forget, though, that the purpose of all these techniques is to allow your Web site to respond dynamically to different users, navigation paths, and events.
The pages of our Course Project site are pretty much static at this point, so our first Project exercise will add some interactivity to the Home Page in the form of a message about a sale that changes as the sale ends.
If you have not yet downloaded, uncompressed, and stored them in a virtual directory at this point, please take the time to do so before continuing on to the exercise.

Course Project - Exercise

Click the Exercise link below to add an interactive announcement to your Course Project home page.
Course Project - Exercise
The next lesson concludes this module.

ASP Course Project - Interactive Message

Constant and Variable Demo

Course Project - Exercise