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MatSelectItem does not update selected value #939

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w26ak opened this issue Oct 2, 2023 · 1 comment
Open

MatSelectItem does not update selected value #939

w26ak opened this issue Oct 2, 2023 · 1 comment
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bug Something isn't working

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@w26ak
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w26ak commented Oct 2, 2023

Reopening #860 since the suggested solution does not seem to work.

The version of MatBlazor: 2.8.0 (2.10.0 has the same bug as well).
Link to Blazorfiddle: https://blazorfiddle.com/s/bdawws66
Below is the code of plain index page:

@page "/"

@if (SelectedProfile != null)
{
    <div>
        <MatSelectItem Items=@Profiles
                        Outlined=true
                        TValue="Profile"
                        @bind-Value=@SelectedProfile>
            <ItemTemplate Context="profile">
                @profile.Id - @profile.Name
            </ItemTemplate>
        </MatSelectItem>
    </div>

    <div class="mt-2">
        <MatTextField Outlined=true
                        TValue="string"
                        Value=@SelectedProfile.Name
                        ValueChanged=@OnNameChanged />
    </div>
}

@code {
    protected List<Profile> Profiles { get; set; }
    protected Profile SelectedProfile { get; set; }

    protected override void OnInitialized()
    {
        base.OnInitialized();

        Profiles = new List<Profile>
        {
            new Profile { Id = 0, Name = "Profile 1" },
            new Profile { Id = 0, Name = "Profile 2" },
            new Profile { Id = 1, Name = "Profile 3" },
            new Profile { Id = 2, Name = "Profile 4" }
        };

        SelectedProfile = Profiles[0];
    }

    protected void OnNameChanged(string name)
    {
        SelectedProfile.Name = name;
    }

    public class Profile
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}
@w26ak w26ak added the bug Something isn't working label Oct 2, 2023
@w26ak
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w26ak commented Oct 4, 2023

Looks like all MatSelectItem, MatSelectValue and MatSelect have the same issue. The main problem is that the value of selected item text is updated using JavaScript and not using C#. As a result one of the ways to fix it is to manually call JavaScript. Not ideal but solves the problem.

Below are two possible solutions I came up with (version 2.10.0):

  1. Extension method for manual update of selected text:
public static class MatSelectItemExtensions
{
    public static void UpdateSelectedText<T>(this MatSelectItem<T> select)
    {
        Type selectType = typeof(MatSelectItem<T>);
        Type itemType = typeof(T);

        // Get currently selected item
        PropertyInfo currentValueProperty = selectType.GetProperty("CurrentValue", BindingFlags.NonPublic | BindingFlags.Instance);
        T currentValue = (T)currentValueProperty.GetValue(select);

        // Call OnValueChanged which accepts old value and new value. Old value does not seem to be used so we can just provide null
        MethodInfo onValueChangedMethod = selectType.GetMethod("OnValueChanged", BindingFlags.NonPublic | BindingFlags.Instance, new Type[] { itemType, itemType });
        onValueChangedMethod.Invoke(select, new object[] { null, currentValue });
    }
}
  1. Custom class derived from MatSelectItem with extra method for manual update of selected text:
public class MatSelectItemFixed<T> : MatSelectItem<T>
{
    internal MatBlazorSwitchT<int> switchTK = MatBlazorSwitchT<int>.Get();

    public void UpdateSelectedText()
    {
        CallAfterRender(async () =>
        {
            await JsInvokeAsync<object>("matBlazor.matSelect.setValue", Ref, switchTK.FormatValueAsString(GetKeyFromValue(CurrentValue), null));
        });
    }
}

For version 2.8.0 the solution is more or less the same:

public static class MatSelectItemExtensions
{
    public static void UpdateSelectedText<T>(this MatSelectItem<T> select)
    {
        // Call OnValueChanged which accepts bool value that indicates whether value is changed
        Type selectType = typeof(MatSelectItem<T>);
        MethodInfo onValueChangedMethod = selectType.GetMethod("OnValueChanged", BindingFlags.NonPublic | BindingFlags.Instance);
        onValueChangedMethod.Invoke(select, new object[] { true });
    }
}

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