当绑定值为null时，会出现WPF datepicker验证错误

问题描述

我有一个WPF应用程序，我使用绑定到实体框架（使用SQL Server）实体的日期字段的日期选择器。我绑定如下：

 < DatePicker x：Name =dtCompleteStyle ={StaticResource FTC_DatePicker}Grid。 Column =2Grid.Row =7Grid.ColumnSpan =3
 Text ={Binding dtComplete，Mode = TwoWay，ValidatesOnDataErrors = True}/> 
  

绑定工作正常，可以更新到实体。

我的问题是，当底层数据库字段为空时，我得到选择一个日期水印，这是我想要的，但是该水印正在被验证并返回，因为不是日期格式。我想保留水印，但是在用户更改输入之前不具有验证触发器。此外，我想保留 ValidatesOnDataErrors = True ，因为我在其他地方使用它来评估业务逻辑。

要查看我的意思是，这是一个使用datepicker与日期的空值的表单，您可以看到验证错误：

调试时的输出窗口提供以下验证转换错误：

有人可以帮助我摆脱这个验证错误，直到用户更改输入？

提前感谢

解决方案

想出来：

绑定到hte datePicker的文本值，所以它试图验证水印文本作为一个日期，但我真正应该做的是绑定到selectedDate属性如下：

 < DatePicker x：Name =dtCompleteStyle ={StaticResource FTC_DatePicker}Grid.Column =2Grid.Row =7Grid.ColumnSpan =3
 SelectedDate ={Binding dtComplete，Mode = TwoWay，ValidatesOnDataErrors = True}/> 
  

现在按照我的要求行事，选择日期水印仍然存在，绑定日期值正常工作。现在太明显了简单修复

I have a WPF application where I am using a date picker that is bound to an entity framework(with SQL server) entity's date field. I bind it as follows:

<DatePicker x:Name="dtComplete" Style="{StaticResource FTC_DatePicker}" Grid.Column="2" Grid.Row="7" Grid.ColumnSpan="3"
Text="{Binding dtComplete, Mode=TwoWay, ValidatesOnDataErrors=True}"/>

The binding works fine and can be updated to the entity.

My problem is that when the underlying database field is null, I get the select a date watermark, which I want, but that watermark is being validated and coming back as not being of a date format. I want to keep the watermark, but not have the validation trigger until the user changes the input. Also, I want to keep ValidatesOnDataErrors=True because I use that somewhere else to evaluate business logic.

To see what I mean, here is a form that uses the datepicker with a null value for the date, you can see the validation error:

The output window when debugging gives the following validation conversion error:

Can someone help me get rid of this validation error until the user changes the input?

Thanks in advance

解决方案

Figured it out:

I was binding to the text value of hte datePicker, so it was trying to validate the watermark text as a date, but what I really should have been doing was binding to the selectedDate Property as follows:

<DatePicker x:Name="dtComplete" Style="{StaticResource FTC_DatePicker}" Grid.Column="2" Grid.Row="7" Grid.ColumnSpan="3"
 SelectedDate="{Binding dtComplete, Mode=TwoWay, ValidatesOnDataErrors=True}" />

This now behaves as I want, the select a date watermark is still there and the binding date value works. Its all too obvious now. Simple fix

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