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
– niao

2010-05-07 07:25:54 +00:00
Commented May 7, 2010 at 7:25 — niao
– niao, Commented May 7, 2010 at 7:25

xkcd · Accepted Answer · 2010-05-07 07:33:17Z

2

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

I think the code above will work for you

answered May 7, 2010 at 7:33

xkcd

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2 Comments

nvtthang Over a year ago

I've tried this situation .It passes on building time but it raises the same error message on runtime.

xkcd Over a year ago

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

Community · Accepted Answer · 2017-05-23 11:47:48Z

1

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.

edited May 23, 2017 at 11:47

CommunityBot

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answered Dec 9, 2010 at 16:10

morphatic

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Comments

Ingo Karkat · Accepted Answer · 2012-12-13 15:33:24Z

1

Try

(model=>(bool)model.isHot)

edited Dec 13, 2012 at 15:33

Ingo Karkat

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answered Aug 31, 2010 at 6:18

Koen Stroobants

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1 Comment

SteveCav Over a year ago

That gave me "Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions."

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