Links
Basic component
| Components/MyComponent.razor
|
<h1>Test</h1>
<p>@ChildContent</p>
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| Components/MyComponent.razor.cs
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public partial class MyComponent : ComponentBase
{
[Parameter]
public RenderFragment ChildContent { get; set; }
}
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| Components/MyComponent.razor.css
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h1 {
color: coral;
}
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| Pages/Index.razor
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@page "/"
@using Component.Components
<MyComponent>
test !!!
</MyComponent>
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| Components/MyComponent.razor.cs
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[Parameter]
public EventCallback<string> Callback { get; set; }
private string description;
private async Task UpdateDescription()
{
await Callback.InvokeAsync(description);
}
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| Pages/Index.razor
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<MyComponent Callback="MyComponentCallback" />
@code {
void MyComponentCallback(string description)
{
}
}
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| Components/MyComponent.razor.cs
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[Parameter]
public string Description { get; set; }
// name of the EventCallback has to be [PropertyName]Changed
[Parameter]
public EventCallback<string> DescriptionChanged { get; set; }
private async Task UpdateDescription()
{
await DescriptionChanged.InvokeAsync(description);
}
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| Pages/Index.razor
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@* two ways binding of the component parameter Description with the local field description *@
<MyComponent @bind-Description="description" />
@code {
private string description = "Text";
}
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Set a value for the component hierarchy from an ancestor component to any number of descendent components.
| Pages/Index.razor
|
@* BtnStyle will be available in MyComponent and all its descendent components *@
<CascadingValue Value="btnStyle" IsFixed="true">
<MyComponent />
</CascadingValue>
@code {
string btnStyle = "btn-success";
}
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| Components/MyComponent.razor.cs
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// match between the cascading value and the cascading parameter is made by the type (string) and not by the property name
[CascadingParameter]
public string BtnStyle { get; set; }
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If the IsFixed value is true (false by default), then receipients receive the initial value but do not set up any subscription to receive updates. In this case, each [CascadingParameter] is lightweight and no more expensive than a regular [Parameter].
So wherever possible, you should use IsFixed="true" on cascaded values. You can do this whenever the value being supplied doesn't change over time.
Component references provide a way to reference a component instance for issuing commands.
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@* without attribute splatting *@
<input id="useIndividualParams"
maxlength="@maxlength"
placeholder="@placeholder"
required="@required"
size="@size" />
@* with attribute splatting *@
<input id="useAttributesDict"
@attributes="InputAttributes" />
@code {
private string maxlength = "10";
private string placeholder = "Input placeholder text";
private string required = "required";
private string size = "50";
private Dictionary<string, object> InputAttributes { get; set; } =
new()
{
{ "maxlength", "10" },
{ "placeholder", "Input placeholder text" },
{ "required", "required" },
{ "size", "50" }
};
}
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