如何在 Blazor webassembly 应用程序中启动时初始化变量? [英] How do I initialize variables at startup in a Blazor webassembly app?

问题描述

在 UWP 中，我会在启动时以编程方式初始化显示变量，以便初始显示是我想要的，例如，基于年份值的值.我无法破解在我其他工作的 Blazor webassembly 应用程序中复制它的位置.我目前设置默认值并要求用户单击一个按钮，该按钮计算并更新我想要显示的值，然后继续.

In UWP, I would programmatically initialize display variables at startup so that the initial display was what I wanted, for example, values based on the day of the year value. I can't crack where to replicate this in my otherwise working Blazor webassembly app. I currently put up default values and ask the user to click a button, that calculates and updates to the values I want to display and on we go.

我本以为有一种标准的、简单的方法可以做到这一点，但考虑到 Blazor 部分是如何动态构建以呈现为网页的，也许不是?谢谢！

I would have thought there's a standard, easy way to do this, but given how Blazor pieces are constructed on the fly in order to render as web pages, maybe not? Thanks!

推荐答案

这不是 Blazor 特有的，但在任何类中，您都可以在组件的构造函数中创建代码/

This isn't specific to Blazor, but in any class you can create code in the constructor of your component/

这里我有一个聊天组件，我把它分解成

Here I have a Chat component, that I break up into

Chat.razor
Chat.razor.cs  

通过添加与组件​​同名的类创建的 chat.razor.cs，然后添加单词 partial 使其成为部分类:

The chat.razor.cs you create by adding a class with the same name as your component, then add the word partial to make it a partial class:

partial class Chat : IBlazorComponent, IBlazorComponentParent, IDisposable

注意:界面仅适用于我的应用程序，我只是显示部分行.你真的需要它:

Note: The interfaces are just for my app, I am just showing the line with partial. really are you need it:

partial class Chat

然后在我的构造函数中创建:

Then in my constructor I created:

public Chat()
{
    // Perform initializations for this object
    Init();
}

我只是调用一个方法，你不必:

I just call a method, you don't have to:

我的初始化方法:

 public void Init()
 {
     // do your initializations 
 }

或者你可以使用 OnInitializedAsync

Or you can use OnInitializedAsync

protected override async Task OnInitializedAsync()
{
    // load the Categories (example)
    this.Categories = await HelpCategoryService.GetHelpCategoryList()
}

或者这是我有时使用的另一个:OnAfterRender

Or here is another I use sometimes: OnAfterRender

protected override void OnAfterRender(bool firstRender)
{
    if (firstRender)
    {
        ...
    }
}

相关文档在这里:

https://docs.microsoft.com/en-us/aspnet/core/blazor/lifecycle?view=aspnetcore-3.1

也许这会给你一些想法.不确定标准版，每个用例都不同.

Maybe that gives you some ideas. Not sure about Standard, every use case is different.

注意:我从未使用过 Blazor Web Assembly，只使用过服务器端 Blazor，所以不确定 WASM 的具体内容，但我知道构造函数适用于任何 C# 类.

Note: I have never used Blazor Web Assembly, only server side Blazor, so not sure what is specific to WASM, but I know constructors work in any C# class.

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