Conversion from type 'DBNull' to type 'String' is not valid

I get an error (Conversion from type 'DBNull' to type 'String' is not valid.) when I try to assign a field value to a text box using the datareader. Is there code that will fix this error? 

0
HallieBerry
10/31/2008 2:31:11 PM
asp.net.getting-started 91979 articles. 3 followers. Follow

6 Replies
718 Views

Similar Articles

[PageSpeed] 17

wrap an IF check around the retrieval and check for DBNull


0
Curt_C
10/31/2008 2:32:41 PM

you'll need to check for null first, before you assign it - -

Something like:

if Not dr("Yourfield") is System.DbNull.Value then...........


David Wier
MCP/ASPInsider
ASPNet101.com - where to look first!
Please Vote for ASPNet101 - 'Best Community Resource'!
Control Grouper - easily control properties for multiple controls with one control!
Calendar Express - The Best HTML Calendar Generator on the web!
(Please 'Mark as Answer' when it applies)
0
augustwind
10/31/2008 2:32:50 PM

have you used the .Tostring qualifier

 ileldname.value.tostring 

 


Liam Mcmullen
0
liammcmullen
10/31/2008 2:33:57 PM

Thanks for your help. Could you please give me an example

0
HallieBerry
10/31/2008 4:43:48 PM

HallieBerry:

Thanks for your help. Could you please give me an example

Show us how you're using the DataReader item, on the line where the code breaks

0
elmoWatson
10/31/2008 10:58:45 PM

Hi

Basically, we just check for to see if the value returned from the Datareader is null.  A simple example would be:

 
while (reader.Read())
{
   if ( reader.IsDBNull(reader.GetOrdinal("columnName")) )
      txtName.Text = reader["columnName"].ToString();
}
 

In the above sample, we use the IsDBNull() method of a datarreader to check if a given column of current record is null.  And, I am passing in the index/ordinal that I've obtained via GetOrdinal(columnName) to IsDBNull(int) method. 

Hope that helps :)


If the answer/reply above helped you, please mark the question as answered. Thank you. =^^=
0
physicsci
11/1/2008 2:18:53 AM
Reply:

Similar Artilces:

Cast from type ''''DBNull'''' to type ''''String'''' is not valid.
How do I avoid getting this error: Cast from type ''''DBNull'''' to type ''''String'''' is not valid. I am trying to get values from the database into a form for updating using a Datareader, SQL is set to allow nulls for certain fields as they are not required but the only way I can get the form to display is by adding a space in SQL. Is there another way around this? Check if it is equal to DBNull.Value first and if it is, don't do the cast.Stanley Tan theSpoke Blog Where in the code does it need to go? I am using the following and it's the profile that isn't always requi...

I get Conversion from type 'DBNull' to type 'String' is not valid.
I get the following errors when I try and access certain pages.  It is caused by not populating all the text boxes with data and subsequent viewing causes these conversion errors.  Does any one else experience this?  How have you guys worked around this problem? Conversion from type 'DBNull' to type 'String' is not valid. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Conversion f...

Conversion from type 'DBNull' to type 'String' is not valid.
On line 65 of Events_Calendar.aspx- <div style="padding: 3px;"> <asp:HyperLink ID="HyperLink1" runat="server" Text='<%#Eval("title") %>' NavigateUrl='<%# "Events_view.aspx?Eventid=" &CStr( Eval("ID"))%>' ToolTip='<%# truncate(CStr(Eval("description"))) %>' /></div> The debugger tells me "InvalidCastException unhandled by user code" I found out that the data entry form for events allows the user to leave the description field empty.  So this translates to NULL in the SQL Server 2005 database.  the NULL value in the description field...

Conversion from type 'DBNull' to type 'String' is not valid...
Thanks for your time.  Getting following error when grid source populates a rows Date field with Null:     - Exception Details: System.InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid.It works works when I filter the nulls out, but I need to show all rows in the grid. Boils down to:  a) How could I maintain a blank value in the grid and cast this properly to include all rows?    < or >  b) Is there a way to default a value that isnt a date (to avoid the null & keep the IsDate logic as is)  c) ...

Conversion from type 'DBNull' to type 'String' is not valid.
 Hello Experts,I am reading data into a datagrid and am checking for nullsHere is the code in the datagrid which checks a function in the code-behind:<ItemTemplate>    <asp:Label id="Label2" runat="server" text='<%# GetPickUpDate(container.dataitem("ActualPickUpDate"))%>'></asp:Label></ItemTemplate> Here is the funtion:Function GetPickUpDate(ByVal DateVal As Date) As String            If Not IsDBNull(DateVal) Then     &nb...

Conversion from type 'DBNull' to type 'String' is not valid.
Hi,it's me again...I'm having error withDim Accesstring As String = ("SELECT     FirstName, LastName, Email, StreetAddress, City, Country, State, Zip, Worknum, googlecheckout, paypal, csftcc, confirmationcode FROM dbo.reservation WHERE (confirmationcode = @concode)")            Dim cmd3 As New SqlCommand(Accesstring, icnnn)            cmd3.Parameters.Add("@concode", SqlDbType.NChar).Value = onlineconfirmationcode.Text   &...

Conversion from type 'DBNull' to type 'String' is not valid #2
I'm getting a error message saying: Server Error in '/' Application. Conversion from type 'DBNull' to type 'String' is not valid. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid.Source Error: Line 113: </h3> Line 114: ...

Conversion from type 'DBNull' to type 'String' is not valid #2
i have with my DB fetch content is Ogject class so i am not use any dataset or datatable but i have problem when field in DB is empty i can insert DBNull in string like this curr.visible = r("visible") curr.title = r("title")curr.description = r("description") curr.price = r("price")   how can i  solve this problem without put if with every insert code fedailr:curr.visible = r("visible") curr.title = r("title")curr.description = r("description") curr.price = r("price") So I assume r ...

Bound TextBox error: Conversion from type 'DBNull' to type 'String' is not valid
 Hi,I use DataSet designer to generate my strongly typed datasets and to bind my FormView to a Business Layer (BLL). The BLL uses the generated Dataset classes. I have a column  in the DB of type string. The column is bound to a textbox like this:Text='<%# Bind("Local") %>'  If the column has a value, thingts work well, but  When the column has a null value, I get the error: Conversion from type 'DBNull' to type 'String' is not validWhat can I do Please? Thanks a lot, I appreciate your taking the time to help me. ...

Conversion from type 'DBNull' to type 'Date' is not valid
I'm using VWD 2005 and have a grid on the page. In that grid, there'sa column that is of date/time type. Nulls are allowed in this column.I'm having problems when trying to edit this date column.I've converted the column to a template and changed theEditItemTemplate from a textbox to a calendar. If a date previouslyexisted for the record being edited, the update action works. If thedate was previously NULL and then a date is chosen via the calendar I get the error. How do I work around this? Charlie Here's my code line:<EditItemTemplate> <asp:Calendar ID="Calendar1" run...

Web resources about - Conversion from type 'DBNull' to type 'String' is not valid - asp.net.getting-started

Resources last updated: 1/23/2016 4:59:19 AM