Component Parameters

Parameters allow Components to pass data from one another. The [Parameter] attribute on a public auto property (no get/set logic) of a receiving Component defines it as a parameter:
PanelBody.cs

public class PanelBody
{
    public string? Text { get; set; }
    public string? Style { get; set; }
}

Shared/ParameterChild.razor

<div class="card w-25" style="margin-bottom:15px">
    <div class="card-header font-weight-bold">@Title</div>
    <div class="card-body" style="font-style:@Body.Style">
        @Body.Text
    </div>
</div>

@code {
    [Parameter]
    public string Title { get; set; } = "Set By Child";

    [Parameter]
    public PanelBody Body { get; set; } =
        new()
        {
            Text = "Set by child.",
            Style = "normal"
        };
}

Pages/ParameterParent.razor

@* this component renders two ParameterChild components *@
@page "/parameter-parent"

<ParameterChild /> @* this component's Title will be "Set by Child" and Body.Text will be "Set by child." *@

<ParameterChild Title="Set by Parent"
                Body="@(new PanelBody() { Text = "Set by parent.", Style = "italic" })" />

Pages/ParameterParent2.razor

@page "/parameter-parent-2"

<ParameterChild Title="@title" /> @* from field *@
<ParameterChild Title="@GetTitle()" /> @* from method *@
<ParameterChild Title="@DateTime.Now.ToLongDateString()" /> @* from implicit C# expression *@
<ParameterChild Title="@panelData.Title" /> @* from panelData's Title property *@

@code {
    private string title = "From Parent field";
    private PanelData panelData = new();

    private string GetTitle() => "From Parent method";

    private class PanelData
    {
        public string Title { get; set; } = "From Parent object";
    }
}