KWWebInvApp/Pages/UserLogin.razor

@page "/userlogin"
@using KWWebInvApp.Data;
@using KWWebInvApp.Services;
@using Microsoft.AspNetCore.WebUtilities;

@inject IAuthenticationService AuthenticationStateService
@inject AuthenticationStateProvider AuthenticationStateProvider
@inject NavigationManager NavigationManager

<PageTitle>User Login</PageTitle>
<MudText Typo="Typo.h3" GutterBottom="true">Enter your credential for verification</MudText>

<EditForm Model="@loginData" OnValidSubmit="SubmitLogin">
    <MudGrid>
        <MudItem sm="12">
            <MudCard>
                <MudCardContent>
                    <MudText Typo="Typo.h4">Login</MudText>
                    <MudText Typo="Typo.subtitle1">Welcome to Merchandise and SAC System</MudText>
                    @if (error != null)
                    {
                            <MudAlert Severity="Severity.Error">@error</MudAlert>
                    }
                    <MudTextField T="string" Label="Username" Required="true" RequiredError="Username is required"
                                  @bind-Value="loginData.username" />

                    <MudTextField T="string" Label="Password" Required="true" RequiredError="Password is required"
                                  InputType="InputType.Password"
                                  @bind-Value="loginData.password" />
                    <MudCardActions Class="mt-5">
                        <MudButton Variant="Variant.Filled" Color="Color.Primary" ButtonType="ButtonType.Submit" Disabled="submitButtonDisabled">@submitButtonText</MudButton>
                        <MudButton Variant="Variant.Filled" Color="Color.Secondary" Class="mx-2" ButtonType="ButtonType.Reset" Disabled="submitButtonDisabled">Reset</MudButton>
                    </MudCardActions>
                </MudCardContent>
            </MudCard>
        </MudItem>
    </MudGrid>
</EditForm>

@code {
    bool submitButtonDisabled = false;
    string? error, submitButtonText = "Login";
    LoginData loginData = new();

    protected override async Task OnInitializedAsync()
    {

    }

    async Task SubmitLogin()
    {
        error = null;

        waitingButton(true);
        var webAuthenticationStateProvider = (WebAuthenticationStateProvider)AuthenticationStateProvider;
        var loginSuccess = await webAuthenticationStateProvider.LoginAsync(loginData);

        if (loginSuccess)
        {
            var uri = NavigationManager.ToAbsoluteUri(NavigationManager.Uri);
            if (QueryHelpers.ParseQuery(uri.Query).TryGetValue("returnUrl", out var returnURL))
                NavigationManager.NavigateTo($"/{returnURL}");
            else
                NavigationManager.NavigateTo("/");
        }
        else
            error = "Invalid username or password. Please try again.";

        waitingButton(false);
    }

    void waitingButton(bool waiting = false)
    {
        if(waiting)
        {
            submitButtonDisabled = true;
            submitButtonText = "Please Wait...";
        }
        else
        {
            submitButtonDisabled = false;
            submitButtonText = "Login";
        }
    }
}