Count calls to method with Dependency Injection

Question

I'm trying to learn about dependency injection. I'm using .net 6.0 Razor Pages and I want to "count", the number of times a method is called via dependency injection. My Index is as following:

public class IndexModel : PageModel
{
    public ICounter _counter;

    public IndexModel(ICounter counter)
    {
        _counter = counter;
    }
    public int Count { get; set; }
    public void OnPostInfo()
    {
        Count = _counter.Calls(Count);
    }
}

My "counter" class, is as following

public int Number { get; set; }
public int Calls(int Number)
{
    return Number += 1 ;
}

And my interface

public interface ICounter
{
   int Calls(int Number);     
}

My Program.cs class

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.AddSingleton<ICounter, Counter>();

My View.

<div class="card">
    <div class="card-body">
        @Model.Count
    </div>
</div>
<div class="row">
    <form asp-page-handler="Info" method="post">
        <button class="btn btn-default">Push to count</button>
    </form>
</div>

It's added as an Transient in Program.cs. The site is updated via a button, and that "works", but it only updates to 1. But then it stops. It doesn't continue to "2, 3, 4" etc when i push the button that uses the OnPostInfo method.

What am i missing here?

Answer 1

Actually it is not caused by lifetime. It dues to the Count value is not passed to the backend, so backend will always get the int default value 0 for Count.

You need set a hidden input or route parameter to pass the Count.

First way to set a hidden input:

View:

<div class="card">
    <div class="card-body">
        @Model.Count
    </div>
</div>
<div class="row">
    <form asp-page-handler="Info" method="post">
        <input hidden asp-for="Count" value="@Model.Count" /> <!--set the hidden input-->
        <button class="btn btn-default">Push to count</button>
    </form>
</div>

PageModel:

public class IndexModel : PageModel
{
    public ICounter _counter;

    public IndexModel(ICounter counter)
    {

        _counter = counter;
    }
    [BindProperty]  //add this attribute to get the Count value
    public int Count { get; set; }
    public void OnPostInfo()
    {
        Count = _counter.Calls(Count);
    }
}

The second way to set a route parameter:

View:

<div class="card">
    <div class="card-body">
        @Model.Count
    </div>
</div>
<div class="row">                  <!--add asp-route-countNum -->
    <form asp-page-handler="Info" asp-route-countNum="@Model.Count" method="post">
        <button class="btn btn-default">Push to count</button>
    </form>
</div>

PageModel:

public class IndexModel : PageModel
{
    public ICounter _counter;

    public IndexModel(ICounter counter)
    {

        _counter = counter;
    }

    public int Count { get; set; }
    public void OnPostInfo(int countNum)   //add parameter here
    {
        Count = _counter.Calls(countNum);   //change here... 
    }
}

Result: