下拉列表中的RequiredFieldValidator 不接受空对象的IntialValue
我已通读此内容，这帮助我缩小了验证范围RequiredFieldValidator 的 InitialValue 属性存在问题。
我的下拉列表是一个对象列表，这些对象由后面的代码填充，如下所示；
brands.Insert(0, Brand.Empty)
cbBrand.DataValueField = "ID";
cbBrand.DataTextField = "Name";
cbBrand.DataSource = new BindingList<Brand>(brands);
cbBrand.DataBind();
其中 Brand.Empty 是空对象类型。
我遇到困难的地方是让 IntialValue 接受空值。例如，InitialValue="" 无法识别列表中的空对象。
谁能指出我解决这个问题的方向吗？
I have read through this which helped me narrow down my validation problems to the InitialValue property of the RequiredFieldValidator.
My drop down list is a list of objects which are populated by the code behind like this;
brands.Insert(0, Brand.Empty)
cbBrand.DataValueField = "ID";
cbBrand.DataTextField = "Name";
cbBrand.DataSource = new BindingList<Brand>(brands);
cbBrand.DataBind();
where Brand.Empty is a null object type.
Where I'm coming unstuck is getting the IntialValue to accept a null value. For instance, InitialValue="" fails to recognise the empty object in the list.
Can anyone point me in the direction of a fix for this?
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空字符串与空值不同。不要向数据源添加空值，而是直接将其添加到下拉列表中，如下所示：
这将向 HTML 选择元素添加一个值为“”的选项，该选项与验证器初始值匹配。
An empty string is not the same as a null value. Instead of adding a null value to your data source, add it to the drop down directly like :
That will add a option to your HTML select element with a value of "", which matches the validators initial value.
哇。我以为在发布这个问题之前我已经非常彻底地搜索了该网站上以前的答案，但我错过了 这个！
答案是将您的
AppendDataBoundItems=true，然后添加一个这里的好处是我的代码隐藏中的列表绑定到对象类型
希望这可以帮助其他遇到这个问题的人！
Wow. I thought I had searched previous answers on this site very thoroughly before posting this question, but I had missed this!!
The answer is to change your
<asp:DropDownList>to have the propertyAppendDataBoundItems=true, Then add an<asp:ListItem Text="" Value="" />between the dropDownList tags and BAM! you can insert a value to the list that does not require the null object inserted in the code behind (which should be removed so that you don't end up with 2 blanks at the start of your list).The benefit here is that the list in my code-behind is bound to an object type
<Brand>, but adding the empty string at the client works fine for client-side validation.Hope this helps anyone else struggling with this problem!