Blazor: BitDatePicker show validation message. How to modify the message?-CodePudding

<BitDatePicker @bind-Value="Model.Date"
                                           AllowTextInput="true"
                                           DateFormat="yyyy/M/d"
                                           GoToToday="امروز" Placeholder="تاریخ را وارد کنید"
                                          Culture="PersianCultureHelper.GetFaIrCultureByFarsiNames()"
                                           Style="width:150px; display:inline-block;">
</BitDatePicker>

(https://i.stack.imgur.com/B45TB.png)

how to change(modify) the default validation message of this component?

I create a class that inherits from "ValidationAttribute" to override the error message by custom regex validation. but two messages show when the input is not valid.

I don't want to use "Require" attribute. it should show the message when the input is not valid.

CodePudding user response：

Not that simple. It's hard coded into the component.

However there is a way.

BitDatePicker is a component that emulates a standard InputBase type component, though it doesn't implement InputBase. The validation message is generated in `TryParseValueFromString' which looks like this:

    protected override bool TryParseValueFromString(string? value, [MaybeNullWhen(false)] out DateTimeOffset? result, [NotNullWhen(false)] out string? validationErrorMessage)
    {
        if (value.HasNoValue())
        {
            result = null;
            validationErrorMessage = null;
            return true;
        }

        if (DateTime.TryParseExact(value, DateFormat ?? Culture.DateTimeFormat.ShortDatePattern, Culture, DateTimeStyles.None, out DateTime parsedValue))
        {
            result = new DateTimeOffset(parsedValue, DateTimeOffset.Now.Offset);
            validationErrorMessage = null;
            return true;
        }

        result = default;
        validationErrorMessage = $"The {DisplayName ?? FieldIdentifier.FieldName} field is not valid.";
        return false;
    }

So we can create a child component and override TryParseValueFromString. Note that you have to "capture" the content generated in the parent and re-gurgitate it in the child.

MyBitDatePicker

@using System.Diagnostics.CodeAnalysis;

@inherits BitDatePicker

@this.ParentContent

@code {
    public RenderFragment ParentContent;

    public MyBitDatePicker()
    {
        ParentContent = (builder) => base.BuildRenderTree(builder);
    }

    /// <inheritdoc />
    protected override bool TryParseValueFromString(string? value, [MaybeNullWhen(false)] out DateTimeOffset? result, [NotNullWhen(false)] out string? validationErrorMessage)
    {
        var isValid = base.TryParseValueFromString(value, out result, out validationErrorMessage);

        //Custom message defined here
        validationErrorMessage = $"The {DisplayName ?? FieldIdentifier.FieldName} field ain't right!";
        return false;
    }
}

You could prevent the problem in the first place by disabling AllowTextInput. The user then can't select an invalid date.