.net - LINQ Replace DBNull With Blank String?
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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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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Apr 7, 2009
Suppose i have two strings which is given below.
CODE:
Where ever i find , it should be replaced one blank line and " replace by "
When i migrated the data from MYSQL to SQL Server 2005, i found few problem in one of the column. In MYSQL indicates as new line and " indicates as ".
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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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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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Sep 29, 2009
So I'm importing Excel data using ADO into a DataTable then pushing out to an Access DB. A couple of the Excel columns have several blank cells that I would like to change to a zero before pushing it out. How can I check/change the DT null values to zero? I've done some searching but was wondering if I could do it without a loop.
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Apr 22, 2012
I am creating a form that is able to update data in SQL server after selecting an MS Access file (.mdb). I am having an issue where the data has a single quote ('). I found out that the solution was to use Replace() - to replace the single quote with two single quotes - Replace(string, "'", "''").Now, for some reason, I am getting an error "Conversion from type DBNull to type String is not valid." Here is the code.
cmd = New SqlCommand("Update Child Set " & _
"TopLevelProject = '" & row("TopLevelProject") & "' ," & _
[code].....
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Mar 8, 2010
Why does the following query raise the error below for a row with a NULL value for barrel when I explicitly filter out those rows in the Where clause?
Dim query = From row As dbDataSet.conformalRow In dbDataSet.Tables("conformal") _
Where Not IsDBNull(row.Cal) AndAlso tiCal_drop.Text = row.Cal _
AndAlso Not IsDBNull(row.Tran) AndAlso tiTrans_drop.Text = row.Tran _
[code]....
Run-time exception thrown : System.Data.StrongTypingException - The value for column 'barrel' in table 'conformal' is DBNull.
How should my query / condition be rewritten to work as I intended?
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May 20, 2010
I've got the following LINQ Statement:[code]invRecord.Pack_Num is a field of type Integer. This means that when I try to access it, if it is DBNull I get a StronglyTypedException. The above code throws this exception. If, however, I remove the "invRecord.Pack_Num = PSNum" and in its place put something like "True", the code works fine. So I guess my question is, why is that that invRecord.IsPack_NumNull() returns False when the value is in fact DBNull and what can I use as a conditional instead? I've been beating my head against the wall for a while now and I can't find a solution to this problem.
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Nov 12, 2011
I've got the following LINQ Statement:
[code]...
invRecord.Pack_Num is a field of type Integer. This means that when I try to access it, if it is DBNull I get a StronglyTypedException. The above code throws this exception. If, however, I remove the "invRecord.Pack_Num = PSNum" and in its place put something like "True", the code works fine. So I guess my question is, why is that that invRecord.IsPack_NumNull() returns False when the value is in fact DBNull and what can I use as a conditional instead? I've been beating my head against the wall for a while now and I can't find a solution to this problem.
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Jan 29, 2008
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.
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Apr 29, 2011
I am querying a datagridview and it works great unless one of the cells has nothing (dbnull). How to over come this?Exceptions: Operator '=' is not defined for type 'DBNull' and type 'DBNull'.
Dim query = From row As DataGridViewRow In DataGridView1.Rows _
Where row.Cells(SelectedColumnIndex).Value = filter _
And row.Visible = False _
Select row Distinct
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May 5, 2009
The file reads in parameters and two of the parameters used to be in Date Format YYYYMMDD but will now permanently be in format YYYY-MM-DD. This change, I believe, is stopping the import of the file from working. I would like to replace the new format YYYY-MM-DD back to YYYYMMDD in the code. If possible I'd also like to see some output so I know that the old format has been replaced with the new format. The code is below. I added the two rows with .replace code in green in expecting that to be enough but it is still not working.
Public
Sub Main()
Dim R1, O1, P1, C1, strDateFrom, strDateTo, strRunDate
As
String
[CODE]...
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Dec 2, 2009
I am trying to sort a LINQ to SQL query based on two fields. The first field is occasionally null which automatically sorts to the top of an ascending query. Is there any way to make the null entries sort to the bottom?
Here is an example:
From x in SampleDataContext.Event _
Order By x.Date, x.Sequence_Number _
Select x.Date, x.Sequence_Number
[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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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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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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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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Mar 22, 2009
I'm working on a .NET application (VB 2008) that gets all of its data from a web-based Django application.I'm using Linq-to-XML and Linq-to-objects in the app.One API call is giving me XML data in the following format that I am loading into an XDocument.
[Code]...
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Feb 28, 2010
Problem: Your task is to take input from the user in string and give the following options to the user in a menu.
1- Find a String
2- Create sub-string
3- Erase a portion of a sting
4- Replace a word in the string
5- Count number of words and characters in the string without spaces.
6- Capitalize first character of each new sentence and convert the rest
of the characters to lower case.
7- Sort all the words in alphabetical order. (Use Bubble sort algorithm to perform sorting).
To perform all the above mentioned tasks you can only use pointers. Create a function to perform every task.
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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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