MudDatePicker DefaultValue plus DateChange - mudblazor

Question

I want to use MudDatePicker element in a way where I need to be able to set a default value on load but at the same time define a onChange event for it. I am trying to do this but error says "The component parameter is used two or more times for this component". Is there a way I can do this?
<MudDatePicker #bind-Date="#DefaultValue.Value" Label="Date" DateChanged="OnDateChange"
Required="true" Class="mb-3" />

Answer 1

If you have a two-way binding in Blazor i.e. #bind-Date="date", you can convert it to a one-way binding with a change event which must set the value. The two-way binding is just syntax sugar and will do the same behind the scene.
<MudDatePicker Date="#_date" Label="Date" DateChanged="OnDateChange"
Required="true" Class="mb-3" />
#inject ISnackbar Snackbar
#code {
DateTime? _date = new DateTime(2021, 12, 24);
void OnDateChange(DateTime? newDate)
{
_date=newDate;
// here you can do something when the date changes.
Snackbar.Add($"Date changed to {_date}");
}
}
Here is a snippet which you can play around with: https://try.mudblazor.com/snippet/mYcPFPvLnlyEHeOF

Answer 2

Remove the DateChanged="OnDateChange" and change #bind-Date="DefaultValue.Value" to #bind-Date="DefaultValue". For the property DefaultValue create a getter and setter. Because you have two way binding using #bind-Date="DefaultValue", the setter part gets called every time the value is changed.
I've added some sample code below:
DateTime? _defaultValue = DateTime.Now;
private DateTime? DefaultValue
{
get => _defaultValue;
set
{
_defaultValue = value;
OnDateChange();
}
}