C#•2y ago

Can someone explain the use of Dispose?

I'm using Blazor and found this code for displaying a live update of The current time. I understand most of it except the use of timer.Dispose(). What would happen if this is not included. I don't notice a difference in performance when not using it.

    string timeString = DateTime.Now.ToLongTimeString();
    Timer timer;
    int interval = 1000
    
    //On page init
    protected override void OnInitialized()
    {
        //callback every 1000 ms
        timer = new Timer(UpdatePage, null, 0, interval);


    }

    //Callback function
    void UpdatePage(object _)
    {
        
        timeString = DateTime.Now.ToLongTimeString();
        //Rerenders the page
        InvokeAsync(StateHasChanged);
    }

    public void Dispose()
    {
        //why?
        timer.Dispose();
    }

    string timeString = DateTime.Now.ToLongTimeString();
    Timer timer;
    int interval = 1000
    
    //On page init
    protected override void OnInitialized()
    {
        //callback every 1000 ms
        timer = new Timer(UpdatePage, null, 0, interval);


    }

    //Callback function
    void UpdatePage(object _)
    {
        
        timeString = DateTime.Now.ToLongTimeString();
        //Rerenders the page
        InvokeAsync(StateHasChanged);
    }

    public void Dispose()
    {
        //why?
        timer.Dispose();
    }

15 Replies

Tvde1•2y ago

hmm Google should have a LOT of answers that explain what Dispose is essentially, some objects may have references to "unmanaged" resources. That means resources that the garbage collector can't clean up For example, if a TCP connection is open, or a file handle

Macke•2y ago

i know that it releases it from the memory. But why do i need to dispose the timer? Shouldn't it dispose automatically?

Tvde1•2y ago

those classes all work the same way, so they have a Dispose() method. That method cleans up those resources It depends per class, but usually if you don't dispose, it means that there will be a memory leak somewhere, or that you'll have many files or connections open Disposing does not happen automatically. The runtime/garbage collector does not know when to close files or connections

Macke•2y ago

Okay. I have defined the function. But it doesn't get called anywhere. So i have to call the function myself right? At least not anywhere i can see

@using System.Threading;
@implements IDisposable

@page "/"


<PageTitle>Index</PageTitle>

<h1>@timeString</h1>


@code {
    string timeString = DateTime.Now.ToLongTimeString();
    Timer timer;

    protected override void OnInitialized()
    {
        timer = new Timer(UpdatePage, null, 0, 1);


    }

    void UpdatePage(object _)
    {
        
        timeString = DateTime.Now.ToLongTimeString();
        InvokeAsync(StateHasChanged);
    }

    public void Dispose()
    {
        timer.Dispose();
    }

    
}

@using System.Threading;
@implements IDisposable

@page "/"


<PageTitle>Index</PageTitle>

<h1>@timeString</h1>


@code {
    string timeString = DateTime.Now.ToLongTimeString();
    Timer timer;

    protected override void OnInitialized()
    {
        timer = new Timer(UpdatePage, null, 0, 1);


    }

    void UpdatePage(object _)
    {
        
        timeString = DateTime.Now.ToLongTimeString();
        InvokeAsync(StateHasChanged);
    }

    public void Dispose()
    {
        timer.Dispose();
    }

    
}

this is the full code

Tvde1•2y ago

I think Blazor disposes for you, becase you have @implements IDisposable at the top

Tvde1•2y ago

https://stackoverflow.com/questions/69655044/blazor-call-dispose-when-components-implements-idisposible

Stack Overflow

Blazor call Dispose when components implements IDisposible

I've done some reading about Blazor component life cycles and noticed that IDisposible can be used to free up memory. To my understanding about IDisposable's Dispose method, it is not guaranteed to...

Macke•2y ago

So blazor calls the method itself?

Tvde1•2y ago

Blazor recognizes that it should do that (because your page is IDisposable) so it will call the Dispose method for you :) so your code looks fine!

Macke•2y ago

ah interesting Would anything bad happen if i decided to not include the disposal? Would the logic stop working after a while?

Tvde1•2y ago

if you removed the @implements IDisposable then the dispose would not be called, correct

Macke•2y ago

Yea, but would the timer bug out after a while since it wouldn't be disposed correctly?

Tvde1•2y ago

not sure what the implication would be in terms of crashes/memory leak, but it's good that you're doing it

Macke•2y ago

ah ok

Tvde1•2y ago

I don't think you'll notice any peformance impact with Dispose btw

Macke•2y ago

I'm not concerned that much about performance rn. I'm still learning the ropes of blazor and i just wanted to understand the code i found thank you for the help man, really appreaciate it

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Can someone explain the use of Dispose?