Convert DBNull To Blank String In Access DB?
May 15, 2010
I'm a new member to this site, and I have been searching for a solution to this problem.. Although I have found variations in the problem, nothing has seemed to work for me. Just started programming last year.
I am trying to populate text boxes in a form based on information from an Access Database. Everything is working, except when there are empty field values; the program then crashes because a DBNull value is returned. I set up an if statement to check the index as the rows are read for DBNull values, the problem is How do I actually change the value in the field from DBNull to a blank string ("") ?? Everything I try gives me an error, most often saying something about setting up an object. The problem happens within my if statement of the do loop...I'm thinking maybe I need to set up parameters ? Or an actual edit session within a datarow variable?[code]...
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Mar 10, 2010
In this example, an error is raised if either row.FirstName or row.LastName are NULL.
How do I rewrite the Select clause, to convert a DBNull value to a blank string ""?
Dim query = From row As myDataSet.myDataRow in myDataSet.Tables("MyData") _
Select row.FirstName, row.LastName
NOTE: Since the DataSet is strongly-typed. I can use row.isFirstNameNull(), but IIF(row.isFirstNameNull(), "", row.FirstName) will not work since all parameters are referenced.
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Oct 12, 2009
I've created a small WPF app in VB9 to catalog our sizable DVD collection. This exercise has been more about learn programming than the need to have a movie database app, but I digress.The SQL database I created has a field for "Genre" that does not have an entry for all the movies in our collection. As such, when I run the method that filters the movie listing by "Genre" the compiler throws the "StrongTypingException was unhandled" error stating "The value for column 'Genre' in table 'Movies' is DBNull.".
I now understand where the DBNull problem comes from and have been searching for several hours to find a VB solution that converts the DBNull fields to strings on the fly during the LINQ query. I've found many solutions people have tried but, since I'm quite new to all this, none of them have worked for me. Pasted below is the method that throws the exception.
[Code]...
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Nov 2, 2009
I am having a problem with the DIM statement. It is saying that it can not convert a DBNULL value to STRING even though there is something in the cell.
[Code]...
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Jan 13, 2010
the code bellow for preview/print .it ok but when i leave the first row ...don't care which cell is blank.The Error was appear"conversion "> =" DBNULL to string "" invalid"IF the cell at the first rows is not blank .i can print that data[code].....
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Jun 5, 2011
I wants to ask how to convert DBNull to Date type?
For Each row As DataRow In dt.Rows
i = 0
Dim array As Object = row.ItemArray
[Code]....
array(i + 10) is datetime type, in the program above, if the Datetime column contains items, it still can run. However, when it loops to a row where the Datetime column does not have value of datetime (or the column is null), then an error " Conversion from type 'DBNull' to type 'Date' is not valid" is occured. I tried to use the if statements as program above but it seems like cannot works.
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Jul 26, 2010
I am attempting to use the DateTimePicker and then add a day to each iteration in a For/Next loop. That seems to work fine and I can verify with msgbox that it is happening. However, I also need to write the date in string format to an Access database using INSERT INTO. However, when the code is ran, I get a "syntax error (missing operator)". Code is below. Can someone help please? I have tried all I know to do.(Please disregard the additional values in INSERT TO, I have verified they are working properly)
[Code]...
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Jun 7, 2011
i am working in windows appl vb.net 08. And i am working in Access DataBase.I have one Table Called "Person" . In this "Person" Table one Column Name Called "OtherName". In this Column binded in one of the Combobox in a Form.But the Problem is "OtherName" Column having the Null Values.Before i bind this Column to Combobox i want to convert this NULL Values to String. Why i need the values in STRING means , In my code i using this Combobox as a filter in SQL Query.If i didn`t change the Null Value to STRING , The Combobox SelectedText or SelectedValue is Showing Nothing. So i am not able to get the Record.
Whn i write a Sql Query to Combobox and apply filter in WHERE statement like Combobox.Selectedtext or Combobox.SelectedValue In "Selected Change Committed Event" then i should get the record in the Output right but unfortunatly i am not getting the Record. The Record Count in DebugPrint showing 0.
[Code]...
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Apr 17, 2009
Is it possible to converty a type System.DBNULL to a string type?
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Mar 26, 2011
I've always been slightly stumped as to why the following happens if I write[code]...
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Oct 1, 2011
I am connecting to a MS-Access 2007 database using VB 2010 and OLEDB. Conducting the following test seems to suggest that MS-Access does not interpret DBNull.Value correctly when sent as a parameter from OLEDB:[code]
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Mar 5, 2012
I have this problem that when the textbox don't have a value I always get this error "Conversion from type 'DBNull' to type 'String' is not valid." [code]...
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Feb 5, 2011
I am receiving the following error "Conversion from type 'DBNull' to type 'String' is not valid" when checking a textedit control to see if it is empty or more than 1 characters in length.
Public Class CustomValidationRule
Inherits ValidationRule
Public Overrides Function Validate(ByVal
[code].....
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Jun 21, 2010
I have the following code:
tb_Job_No.Text is a combobox
This is the code:
Public Sub RepCD_process()
ssql_Job = "SELECT * FROM Rep_Dist"
ssql_Job = ssql_Job + " WHERE (Job_Number = '" & tb_Job_No.Text & "') "
Dim Main_Form As New Main_Form
[Code] .....
Can't seem to get pasted this, when it is remark out all works. How to correct this and get data into the listview?
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Feb 16, 2008
Populating a datatable from Access gives me this exception where a record has an empty field. How do I handle it?
System.InvalidCastException was unhandled
Message="Conversion from type 'DBNull' to type 'String' is not valid."
Code:
Private Sub ShowData()
lblCustNo.Text = CStr(dtOrderEntry.Rows(intCurrRow)("CustNo"))
lblCustName.Text = CStr(dtOrderEntry.Rows(intCurrRow)("CustName"))
lblAddr1.Text = CStr(dtOrderEntry.Rows(intCurrRow)("Addr1"))
lblAddr2.Text = CStr(dtOrderEntry.Rows(intCurrRow)("Addr2"))
[Code] .....
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Oct 9, 2010
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim connectionString As String
Dim cnn As OleDbConnection
Dim adptr As OleDbDataAdapter
[code].....
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Aug 13, 2010
I am trying to populate a textbox.text with a value with a record from a datagrid. I can get my value from the datagrid by the following
Dim eRow As Integer
eRow = datagrid.CurrentRow.Index
txtSelecteditem.Text = datagrid.Item(0, eRow).Value
This all works fin when there is a value in the cell it is picking up. However, I hit a problem when this filed is blank.
The error I get is: Conversion from type 'DBNull' to type 'String' is not valid.
How can I get the textbox to populate with null if the field is null.
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Jun 21, 2010
Basically I would like to have an sql statement which selects all the bookings from a table in microsoft access callled tblBookings where a certain date (selected by a datetimepicker) selected in vb.net.
The field the date is in access is bookingsdate and that is a shortdate aswell.
The problem is that even if the dates are the same the headers come up in the datagridview but no data.
This is my code:
Dim con As New OleDb.OleDbConnection
Dim OleDBCon As System.Data.OleDb.OleDbConnection
Dim ds As New DataSet
[Code].....
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Aug 13, 2011
I want to add a blank value to a field in access database with vb 2008 command.
Problem 1: Here is my code, it shows conversion to string not possible errors
Private Sub btnRedThrow_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRedThrow.Click
Dim dbCnct As New DBUtills
[Code]....
notice the fifth and last value is empty. But it is not being added into the database, how do I do that?
Problem 2: Why does an additional field from my access database disappear even after I manually created the field?? (access database 2003 version, extension is .mdb) I'm using visual studio 2008
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May 16, 2009
I have searched all over the forums and not found an answer to my question. My question is how do i write to an access database at runtime. The database is also created at runtime. I have a dataset loaded with a table that i needs to be written to the database. how would i write each row of my dataset to my database? Sorry if this sounds a little jumbled together it is late and i am tired. If it is unclear you can ask me and i will answer any questions you have about my question.
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Jul 28, 2011
Anyone know why the following is not working?
[Code]...
I get no errors, it just returns a blank string.
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Feb 10, 2009
How can we remove all blank spaces from end of the string fox example the string name before remove space
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Jun 12, 2012
I have a string which contains many rows of data which has been converted from a datatable. The last row of my string has nothing within it, no spaces or anything. How can I get rid of this row? I have tried regex, but cant seem to get anything that does the job. I am writing in VB.[code]...
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Apr 7, 2011
I have problem insert records from my vb application to my access .mdb dataabse with all columns set as not allow zero length string and when I insert a records in which one of the column is null value it show allow zero length string error any idea how to create a code in visual basic in which allow zero length without change the configuration of the database?
For example my record have job_no name station 1 des 2 albert so I need to pass job number 1 to my access database but came out with error zero length string off course my access database is set no all to do so but I have my reason is that any sample code to force to accept blank strings?
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Aug 16, 2010
I'm implementing a feature which reads comma separated txt file from server(one line at a time). Format of file is fixed, There are 3 columns on each row. After reading the row from file I insert it in a database table. But first value of each row aoutomatically appends two blank spaces, even if there are no blank spaces at the begining of each row. I tried to use "TRIM/LTRIM/Replace" to remove blank spece from the first value of each row, but didn't succeed.
[Code]...
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Jun 10, 2010
My Requirment is to Leave Blank space to the right of the each Lable (String) in Chart in SSRS.
Using Custom VB.NET Function, i want to Pass String Lable to VB.NET Function and then Function Return String with Padding Blank Space to the right of String.
Example :Lable String is : "United States of America"
My Lable output should be : "United States of America "
How can we achieve ?
Let me know if you need mor information.
is there any other way to achieve this ?
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Sep 5, 2010
i have a small program to run through a log file and extract data from it which works, but the array it puts out has a blank value before and after the actual data values, and it confuses me why that happens, i dont really understand why and was hoping someone here knew! the parts of the code related are below
Dim rgxSessionStart As New Regex("^Session Start: [A-Z][a-z][a-z] ([A-Z][a-z][a-z]) (dd) dd:dd:dd (dddd)")
Dim substrings() As String
substrings = rgxSessionStart.Split(LineIn)
a sample line that it would match is Session Start: Sun Aug 22 00:00:00 2010 which WORKS, but the values of the array are "","Aug","22","2010","". so its not a critical problem because i can still get the data from it, but those blank values are puzzling and i feel like maybe im doing something wrong with the syntax or method for them to be there.
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Aug 25, 2011
I use an OLEDB connection to read from an excel database, and this loop to read in all of the data from each of the columns
While reader.Read()
For i As Integer = 0 To reader.FieldCount - 1
temp = reader(i).ToString + ControlChars.Tab
output_file.Write(temp)
[code]....
Some of the columns contain date information, which are read in fine (usually as a string "2/20/2011" or so), but the headers of those columns are read in as a blank "". The headers for all the other columns read in fine, but not for the date containing columns.
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Mar 22, 2010
I'm trying to add a new record to my database but i keep getting the message - "conversion from type DBnull to type string is not valid". I think its something to do with the Employee ID when VB attempts to save it to the database my code is below
Imports System.Data.OleDb
Public Class Add
Private Sub DisplayRow()
[Code]....
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Feb 23, 2010
I have the following query
Dim get_rmf_2 = From rmf In t_rmf _
Where rmf!NIVP = nivp_rap
When i run it i get an error :
Operator '=' is not defined for type 'DBNull' and string "test".
I suspect this is because the column "NIVP" in the datatable contains null values, I've tried yhe same thing without null values and it works.So how can i make this work ? ; the column "NIVP" really has a row "test" , and a normal SQL query works fine.
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