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Unable to cast object of type 'System.DBNull' to type 'System.Byte[]

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Thomas
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Thomas asked on 27 Aug 2009, 07:20 PM

I am using RadBinaryImage control with SqlDataSource. If the VarBinary field contains a NULL value I am getting this error:  “Unable to cast object of type 'System.DBNull' to type 'System.Byte[]' “.

My understanding is that a NULL field should be cast to  a null or empty byte[].

Can someone please show me how check if the supplied value is of type DBNull and how to change it to appropriate empty byte array or null in C#?


Thanks,
Thomas

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BaiH
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answered on 28 Aug 2009, 06:29 AM
Hey Thomas, I think you have missed the first thread in this forum ;) Here is a link.

--BH
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Thomas
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answered on 29 Aug 2009, 03:44 AM
I have read the first thread and I understand that the field should be cast to null or empty byte[]. My question was: how to do it.  I would appreciate if someone would help me with an example in C# .

Thanks,
Thomas
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Growls
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answered on 31 Aug 2009, 05:11 AM
to do it in markup:
 <telerik:RadBinaryImage runat="server" ID="rbi" DataValue='<%# ((System.Data.Linq.Binary) Eval("imageFull")).ToArray() %>' /> 

or do it dynamically:

var product = (from p in products 
               select p).First();//.First() = LIMIT 1 in sql, which in turn makes the product variable singular and usable like this: 
rsi.DataValue = product.imageFull.ToArray(); 



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Thomas
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answered on 07 Sep 2009, 02:51 AM
Thank you Craig. This is what I was looking for.
Thomas
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Bodie Sullivan
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answered on 17 Sep 2009, 08:15 PM
I am having the same issue but my project is in VB using .Net 2.0... What would the syntax be for VB with out using LINQ to convert a null value in the markup?
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Derek
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answered on 15 Nov 2009, 11:48 PM
I'd like to see the solution in VB (and without using LINQ) as well. Anyone?
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Ilya Tryapitsin
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answered on 25 Dec 2009, 09:19 AM
For VB without LINQ you can use IIf function.
For example:
 < asp:Repeater ID="Repeater1" runat="server" DataSourceID="SqlDataSource1">     
    <ItemTemplate> 
    ...   
        <telerik:RadBinaryImage ID="RadBinaryImage1" runat="server" DataValue='<%#IIf(Typeof(Eval("photo")) is DBNull, Nothing, Eval("photo"))%>' /> 
    ...   
     </ItemTemplate> 
 
 
 

 

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Richard
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answered on 23 Mar 2012, 07:42 AM
I think you should check the value containing DBNUll or not , You can check DBNull value using System.DBNull.Value , find the full source code to check DBNull value here :

http://net-informations.com/csprj/ado.net/cs-dbnull.htm

algr.

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syeada sanjida
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answered on 29 Jan 2015, 12:05 PM
 when i can editing this message show .why this problem show unable to cast object of type system.dbnull to type 'system.byte[]
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Thomas
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Growls
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