How to binding to bit datatype in SQL to Booleans/CheckBoxes in ASP.NET MVC 2 with DataAnnotations

Question

I've got problem with binding data type boolean to checkbox in MVC 2 data annotations Here's my code sample:

label>
Is Hot
</label>
<%=Html.CheckBoxFor(model => model.isHot, new {@class="input" })%>

It always raise this error message below at (model=>model.isHot).

Cannot convert lambda expression to delegate type 'System.Func<Framework.Models.customer,bool>' because some of the return types in the block are not implicitly convertible to the delegate return type

Cannot implicitly convert type 'bool?' to 'bool'. An explicit conversion exists (are you missing a cast?)

Please suggest me how can I solve this problem?

Thanks in advance.

what is the type of your isHot property? – niao May 07 '10 at 07:25 — niao, May 07 '10 at 07:25

score 2 · Answer 1 · answered May 07 '10 at 07:33

2

<%=Html.CheckBoxFor(model => model.isHot ?? false, new {@class="input" })%>

I think the code above will work for you

answered May 07 '10 at 07:33

xkcd

2,538
11
59
96

I've tried this situation .It passes on building time but it raises the same error message on runtime. – nvtthang May 08 '10 at 06:34
1

<%=Html.CheckBoxFor(model => model.isHot.HasValue ? model.isHot.Value : false, new {@class="input" })%> – xkcd May 08 '10 at 10:49

score 1 · Answer 2 · edited Dec 13 '12 at 15:33

1

Try

(model=>(bool)model.isHot)

edited Dec 13 '12 at 15:33

Ingo Karkat

167,457
16
250
324

answered Aug 31 '10 at 06:18

Koen Stroobants

11
1

That gave me "Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions." – SteveCav Jul 26 '13 at 03:20

score 1 · Answer 3 · edited May 23 '17 at 11:47

Your problem is that the Entity Framework has two ways to map the Bit datatype in SQL to Boolean. If you allow null values in your database then the datatype is Nullable which theoretically has 3 values: Null, False, True. This can't be cleanly mapped to Bool which only has 2 values. See more info here: ASP.net MVC CheckBoxFor casting error

The simple answer is to go into your database and disallow null values on your Bit field.

How to binding to bit datatype in SQL to Booleans/CheckBoxes in ASP.NET MVC 2 with DataAnnotations

3 Answers3