I'm trying to handle DBNull exception while reading data from database. It's my code:
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Dim SQLRDAs SqlDataReader
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val1= GetStringFromDB(Trim(SQLRD("Name")))
val2= GetStringFromDB(Trim(SQLRD("Level")))
[Code]...
But still I get Conversion from type 'DBNull' to type 'String' is not valid. error.
Is this class normally slow or maybe there is something in my process making it slow.I have to import 170,000 rows of data from a fixed length text file into a SQL table. It takes about 2 minutes in a DTS package on SQL server 2000. But we are migrating to a SQL 2008 server and since this code has several manual steps and does not manipulate the data I thought it would be easier to use the TextFieldParser object to handle reading in the data.
Here is the code:
CODE:
I have built everything for Beta one and I thought I had done very well until and Exception happens when I try and run it. Please could someone take a look at this and see if you know whats causing it:
Message: {"No value given for one or more required parameters."} Error -2147217904 Item: In order to evaluate an indexed property, the property must be qualified and the arguments must be explicitly supplied by the user. I don't know whether more info is required from the error but it happens on this line:
DReader = DSelectCommand.ExecuteReader
[Code]...
I have checked the database is in the target location and the table names and column names are all correct.
This is what I'm doing to select and display 3 columns of my datatable in GridView:
Dim myCustomers = From Cust In myDataset.Customers _
Select CustomerId = Cust.CustomerId, _
CustomerName = Cust.CustomerName, _
ExpiryDate = Cust.ExpiryDate
DataGridView1.DataSource = myCustomers.ToList
The expiry date has null values in many records whose expiry date is not set.On executing the query I get runtime error:System.Data.StrongTypingException "The value for column 'ExpiryDate' in table 'Customers' is DBNull."
Obviously, my LINQ query is wrong or incomplete, but I am not able to figure the way to do it correctly.
how can i display data from a sql database in a listbox?
View 2 RepliesI was working on a project in my VB.NET Express and suddenly my code that was working fine and starting up as normal gave me this error:
{An error occurred creating the form. See Exception.InnerException for details. The error is: Corrupt .resources file. Got an unexpected EndOfStreamException while trying to read the ResourceReader header.}
When I'm trying to run my application, it doesn't open my main form.
Private Sub frmAttendace51_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'clear data set of any existing data
objDataSet.Clear()
'fill schema
[Code]...
reading and modifying data from database
View 4 RepliesI made a query in MS Access using fields from multiple tables. I want to display stuff from it into a listbox on the form and then I need to save stuff back too it also. But I'm obviously doing something wrong cos I keep getting the error: "The Microsoft Jet database engine cannot find the input table or query 'Today'. Make sure it exists and that its name is spelled correctly." [code] Also, I have written further down objDataSet. Tables("Today's Absentees") and "Today's Absentees" is a query not a table, what needs to be written instead?
View 3 RepliesHow to read data, submit queries from vb application to a remote machine running sql server. note: I have created a complete functional version of a stock control system with the database residing in the local machine. I just need the basic concept of interacting with remote databases that's all. Do we have to use sockets to read/send data ?
View 2 Replies1) i want to make my login page (which talks to a sql table called logins) my first page and it authenticates to that database and doesnt let you in until correct credentials are entered. ? not sure how
2) I have a Checklistbox that is populated with names - ( i want to be able to populate a database called members with those names(Firstname & Surname Only) and from a New members form populate the same members details into the members database this time including address email tel etc etc ....
3) create a delete button that will delete the information from the database and from the checklistbox1 (this is in case the member leaves the club).
4) how do you create trial versions keys etc ...
5) change a progressbar timer to last an 1½ and show hours minutes seconds but once the button is hit to stop the timer it automatically resets to zero.
I'm reading data from a .mdb access database to a form in my app. However the text is sometimes becoming scrambled as shown belowDatabase:Quote:The resistance of a 2.5mmonductor of length 8m and resistivity p = 1.72
View 6 RepliesI ran into an interesting dilemna today. I have a function that handles information and checks for duplicate values, then returns the next number that is not a duplicate. So, I have something like this:
Public Function GetNextNonDuplicateNumber(NumberToCheck as Long) as Long
//the non-duplicate the function will return
Dim NonDuplicate as Long
'duplicate
If CheckForDuplicate(NumberToCheck) = True Then
Throw New DuplicateException()
[Code] .....
As you can see, I want to handle the exception specifically, but I also want to throw it when I'm done because I want to alert other code outside the function. The problem is that simply throwing it exits out of the function with a null value.
i am using data grid view.if i loaded this data grid view with about 15 and above rows and traverse in data grid view by pressing down arrow key then an unhandeled exception throws.The unhandled exception is as below value of '176' is not valid for 'value' .'value' should be between 'minimum' and 'maximum' parameter name value..
View 2 RepliesI am using VB.Net code to print barcode label in Zebra TLP 2844 printer. And the printer is connected to system by USB port. When i execute the code i get an error "Invalid Parameter : Name handle" in the line outFile = New FileStream(_SafeFileHandle, FileAccess.Write) . As this is a USB port So i shared the printer and used the UNC path. But still i get the error. Below is the complete code
[Code]....
I have login system and also I know how to get 1 exact row from mysql but how can I create a table which will be filled with values from mysql table?
[Code]...
how to perform the database operation such reading data and using them for comparison within the VB programming..
Please guide me with explanation as i have very little knowledge regarding the database operation...
i am using VB.Net 2008 as frontend...and MS SQL Server 2008 (express edition ) as back end...
I have some trouble with opening a excel sheet and getting some data out of it.
I want my program to have a button, when pressed, gives a "select excel file" popup and then load the data from some cells into my sql database.
So, when opening a excel file the program should get the data from cell D3 to D8 and put that into the sql database.
I now have the following, but that will only open the excel file.
Public Class Form1
Dim oConn As ADODB.Connection
Private Sub ConnectDB()
[Code]....
What do you think is the best way of handling a Timeout Expired exception?
View 4 RepliesI want to force a calling method to implement exception handling.
Java forces a calling method to implement exception handling where it calls another method that thorws an exception.
Does VB.Net have the same mechanism?
I am trying to get a list of files using this line of Dim files() As String = IO.Directory.GetFiles("D:", "*.*", SearchOption.AllDirectories)But it errors out on folders that are inaccessible, like the RecycleBin folder & the program stops. So how do I get a list of files in all folders, while skipping the inaccessible one
View 1 RepliesI have searched other forums, google, etc. and have not find a solution. I am creating a VB.NET application using Visual Studio 2010. My application runs fine inside the IDE. Outside of the IDE, it crashes immediately with an OOM exception. I have compiled the program in both VS 2010 and VS2008. The outcome is always the same. I increased my Desktop heap to 12288 meg from 3072 meg thinking that was the issue, but the outcome is the case. Although the increase does improve my response in the IDE. The error is also being reported as related to mscorlib.dll; and my version is for 2.0 framework is 2.0.50727 and for 4.0 framework is 4.0.30319. I am running Windows XP/SP3.
View 13 RepliesIs there a way I can catch and handle two different exceptions within the same exception type? For example:
Try
' My code
Catch ex As System.Net.WebException
End Try
I have 2 different exceptions that are System.Net.WebException. I want to handle them different ways. Problem is the catch block above catches them both. Is there a way I can determine if which of the two it is and handle them differently?
Is there a way to handle quotes with a field in text tab delimited file example:"This program works "really" nicely and is helpful" my reading and understand thus far is that while the file is tab delimited fields can also begin and end with quotes. Therefore is a field contains a quote it gets interpreted as end of field.[code]
View 9 RepliesI'm reading a xml document via a text reader, this is my code
[Code]...
I am recieving this error on this line
ctl.Value = CType(Me.Value, DateTime)
Conversion from type 'DBNull' to type 'Date' is not valid.
I am using Data Grid View and This is a calendar Type Column
I have a little problem regarding the use of DBNull, NULL etc. in VB.net in combination with SQL Server 2k.
More specifically, I want to do something along the lines of this:If x = 0 Then
x = DBNull.Value where x is declared by Dim x as Object. I would rather use Double, but I can't assign DBNull.Value to this, and using Object works quite well, too. But every time I hit this condition, I get an exception: A first chance exception of type 'System.InvalidCastException' occurred in Microsoft.VisualBasic.dll This is not a major show-stopper, since the database value I write x to in the next step, is NULL by default - most of the time! So I need the ability to write NULL to it. If that was not the case, I would have been able to work around this by catching exceptions, I think - but sadly, this isn't really of use then.
I'm using VS2010 and SQLServer 2008. I'm trying to test for DBNull in datafields, but every formulation of a test I have imagined (or found) throws an error. Specifically,"The value for column 'ColumnName' in table 'TableName' is DBNull." (system.data.strongTypingException).Well, not too helpful. I know it's DBNull, and I want VB to recognize this.Here is what I've tried so far (all with the same result).
[code]...
I have a SortedList
Protected _Items As New Generic.SortedList(Of String, _Control)
I am adding items into this SortedList
_Items.Add(_key, _Control)
[code].....
Exception While Reading Excel Sheet Drop Down Value...
View 3 Replies