If you are giving interview on Blazor, you will face this question. We can communicate child component to parent component using EventCallback.
We will create one Child Component with Textbox as Input and Button. Whenever user will pass the input on textbox and click on Button. Then input text will display on Parent Component.
Child Component code snippet
<div>
<input type="text" @bind="@message" />
<button @onclick="DisplayMessage">Click Here</button>
</div>
@code {
[Parameter]
public string InputParam { get; set; }
[Parameter]
public EventCallback<string> OnClickCallback { get; set; }
private string message;
private async Task DisplayMessage()
{
await OnClickCallback.InvokeAsync(message);
}
}
Parent Component code snippet
@page "/"
<PageTitle>Index</PageTitle>
<SurveyPrompt InputParam="message" OnClickCallback="@ShowMessage" />
<p>@message</p>
@code
{
private string message;
private void ShowMessage(string _message)
{
message = _message;
}
}
Summary: In the above demo, we saw that using EventCallback, we can communicate from child component to parent component.
If you are looking how to trigger Parent to Child component, then please read this post
Chandradev's Blog 