How do I create a custom component in Blazor?

You can create custom components in Blazor and reuse them across the application. You can also create a razor component in a shared or custom folder, and define it. Then, the custom component like HTML tag (FileName) can be used in the application.

[HeaderComponent.razor]

@using System.Globalization

<h1 style="font-weight:@fontweight !important">@_headingText</h1>

<form>
<div>
     <input type="checkbox" id="fontweight"
               @bind="bold" />
      <label class="form-check-label"
               for="italicsCheck">Use Bold</label>
</div>

<button type="button" class="btn btn-primary" @onclick="UpdateHeading">
        Update Font</button>
</form>

@code {
    private static TextInfo _tinfo = CultureInfo.CurrentCulture.TextInfo;
    private string _headingText =
        _tinfo.ToTitleCase("welcome to blazor!");
    private string _headingFontStyle = "normal";
    private bool bold = false;
    private int fontweight = 500;
    public void UpdateHeading()
    {
        //weight = 900;
        fontweight = bold ? 900 : 500;
    }
}

//parent component

[index.razor]

@page "/"

<h1>Hello, world!</h1>

Welcome to your new app.

<SurveyPrompt Title="How is Blazor working for you?" />

<HeaderComponent />