How to handle null value

I got trouble with System.Null.ReferenceException. Please guide me how to manipulate it.

Below is my error code line, when the result of my query returns null value.

string FATypeName = SelectCommand.ExecuteScalar().ToString().Trim();

Thanks,

string FATypeName = SelectCommand.ExecuteScalar()
if ( FATypeName!=null )
{
FATypeName=FATypeName.ToString().Trim();
}
else
{
FATypeName=String.Empty;
}

How to handle NULL fields-error with fill method

I have a data adapter that is using a stored procedure and when I get to the fill method to fill a dataset I get the following error
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
The results of the procedure has 6 columns by 50 rows with some NULL field values throughout so think the NULLs are causing the problem. Just wondering how to handle this? Thanks Paul.Fixed this problem. Since a change was made to the procedure, reconfiguring the data adapter cleared the problem.

How to Handle Error Message: "Login failed for user (null). Reason: Not associated with a

I'm running WinXP and using "Visual Studio 2005". To make a long story short, my "Default.aspx" page is using a GridView to display data which is being read from a Windows 2000 DB server. When I run the app under the IDE all works fine.

I copied the 1 file and put it into my folder as, "C:\Inetpub\wwwroot\default.aspx". When it loads I receive the error message, "Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection."

I'm frustrated with Studio Express 05 and will not bother with it again until Microsoft fixes this deployment issue. Can any one PLEASE help me???As you surely understand, this is a question of Access Premissions. When you write "Windows 2000 DB server", do you actually mean SQL 2000 Server? Assigning permissions correctly to the '<machinename>\ASPNET' account can be a bit difficult to grasp sometimes. It would help if you described your exact setup (what is installed on which machine). Example:
- Asp.Net 2.0 version 2.xxxxxxxxxx installed on machine YYYY running OS Windows XP Pro with 'IIS X.X'
- SQL Server version XXXX running on machine ZZZZ running OS QQQQ.

swep wrote:

I'm frustrated with Studio Express 05 and will not bother with it again until Microsoft fixes this deployment issue. Can any one PLEASE help me???

Your error SCREAMS "bad/improper connection string", so i wouldn't be so quick to blame a "deployment issue"
Application created on (my machine):
- Asp.Net 2.0 version 2.0.50215.44 running OS Windows XP Pro SP 2 with 'IIS 5.1'

Accessing database on:
- SQL Server 2000 Enterprise Edition running OS Windows Server 2000.

I'm really stuck...Any help you can offer would be greatly appreciated.
You must put in a valid connection string, because that is what the error is telling you
http://www.connectionstrings.com

I'm really lost right now and need some expect advice. You mentioned in the ASP.NET forum,

"You must put in a valid connection string, because that is what the error is telling you"

If my connection string is wrong then why can I connect to the db server within Visual Web 2005 just fine? My web.config file contains my connection as,

add name="WebConnectionString" connectionString="Data Source=NAME OF SQL SERVER;Initial Catalog=NAME OF TABLE;"

Could it be that I created this in .net framework 2.0 and it is querying a database in the .net framework 1.1?

hello.

maybe the problem is related with the fact that the asp.net user hasn't enough permissions to access the database (you might not have faced this problem because when you use the internal server it'll use the credentials of the active user to process the request - this does not happen when you use IIS: in this case, i't use a specific account for accessing the db).

How to handle a integer null value in a (.xsd) dataset

Hi.

I want to pass a null value to an integer in a (stored) dataset. The column in the database allows null values, but the dataset throws an error. (VS2005)

Goos van Beek

If column in DataTable allows NULLs, you could assing value using DBNull.Value, not Null

Thanks for responding, Val.

How can I pass a DBNull value to the dataset? The user deletes an integer value in a bound textfield and the result is a frozen application.

Of course I can use unbound fields, which I usually do, but I have chosen for the easy way this time :-)

Goos van Beek.

In a case of binding, I do not think you have much control, but I believe application should not freeze in this case anyway. Do you get any exception? Do you trap any exceptons but do not handle them? In a case of unbound controls, you could assign value using next code, but you have to know index of the row that require the change

MyDataTable.Rows(IndexOfTheRowHere).Items("MyColumn)=DBNull.Value

Actually the application doesn't freeze, but the cursor can't leave the field until there is a integer value typed in the field. And that's the problem when the value should be null (or dbnull)

I know the record index, but i can't update a single value of that row.

this.MyDataSet.Tables[0].Rows[idx].Items["MyFieldName"] = DBNull.Value; doesn't work, because the there is no defenition for 'Items'

I can update the value in the underlaying database table, but not in the dataset.

Goos van Beek.

uhmm... (a little idea...i don't now how it fits your needs)...

you can set in design time a default value for your column...this value is never used by your application (e.g. invoice total value cannot be negative and you can use -1).

In runtime when the user clean the column you can set somthing like this

this.MyDataSet.Tables[0].Rows[idx].Items["MyFieldName"] = myDataset.MyTable.MyColumn.DefaultValue

Thanks for responding, Bob.

Sometimes you don't want a default value, although not in the userform.

I changed the datatype in the dataset from System.Int32 to System.String. This allows me to enter a null value in the field. The value in the table is updated by a SqlCommand. Only this is not what I want...

this.MyDataSet.Tables[0].Rows[idx].Items["MyFieldName"] = myDataset.MyTable.MyColumn.DefaultValue; doesn't work, because the there is no defenition for 'Items'

Isn't there a way to adapt the default behaviour of the dataset to handle null values for an integer?

how to handle "" in select statement?

How to handle last name like O'Connor, D'Avino?
If I use:
Select * from tblPeople where LastName = ' & strLName & '
I got error if strLName = O'Cononr

If you stick with this way of doing it (concatenation), you will need to double up the single quotes before you insert. Check out this tutorial:
http://aspnet101.com/aspnet101/tutorials.aspx?id=2
However, for many reasons (security being one of the most urgent), I'd suggest learning about parameterized queries - then, you don't need to worry about such stuff:
http://aspnet101.com/aspnet101/tutorials.aspx?id=1