Blazor - cannot convert from 'method group' to 'EventCallback'
Solution 1
You were close:
<ChildComponent Item="someModel" T="SomeModel" DeleteCallback="OnDeleteSomeModel" />
@code {
SomeModel someModel = new SomeModel();
void OnDeleteSomeModel(SomeModel someModel)
{
...
}
}
The EventCallback uses a generic type and blazor cannot infer it if you don't pass the type to the component.
This means that if you have a EventCallback<T>
you need to pass the value of T
to the component e.g. T="SomeType"
.
Solution 2
I've experienced that the syntax was spot on and still getting this error.
Restarting Visual Studio 2019 solved the problem for me. Cleaning and rebuilding was not enough.
Solution 3
For some reason Visual Studio kept a previous signature I had used. Cleaning, restarting, emptying bin/obj folders etc did not work. I had to rename the method, which worked for me.
Solution 4
The following syntax worked for me:
// in the component (C#):
[Parameter]
public EventCallback<MovingEventArgs> OnMoving { get; set; }
// on the using side (Razor):
OnMoving="(Component.MovingEventArgs o) => OnMoving(o)"
// on the using side (C#):
protected void OnMoving( Component.MovingEventArgs e ) {
}
There seems to have been a change and the documentation is not up to date. This event is also using custom event arguments.
Solution 5
In my case I declared a nullable EventCallback?
- you can't do that.
Comments
-
scottdavidwalker almost 2 years
I'm having an issue with a basic blazor project. I have a parent component and a child component with an event callback where I want it to pass back a type of T. The issue I'm having is that I have an error about converting MethodGroup to EventCallback. If I convert this to using Action then it works but I can't do it async which isn't ideal. Any ideas what I'm doing wrong?
Parent
<Child DeleteCallback="@OnDelete"></Child> public async Task OnDelete(T item) { }
Child
@typeparam T [Parameter] public EventCallback<T> DeleteCallback { get; set; } <a @onclick="() => DeleteCallback.InvokeAsync(item)"></a>
I've added a repo here explaining the problem. Looking at the Issues for Blazor, this should;ve been fixed in 2019. https://github.com/scott-david-walker/EventCallbackError