.net - Filtering DBNull With LINQ?
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 13, 2011
I am using LINQ - VB.Net I want to filter my List object by passing String object in the where.
Dim _permittedTransactionCodes As List(Of String) = Nothing 'String object
it is populated with data.
Dim tap100transCodeInfos As List(Of Tap100transCodeInfo) = _dal.GetActiveTap100transCodeByHdrScreenCde(UCase(screenId), "TRAN_CDE")
i am trying something below, but not getting the filtered results
tap100transCodeInfos.Where(Function(x) _permittedTransactionCodes.Contains(x.TranCde))
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Mar 1, 2011
I have list object and I need to check id in a comma separated string using LINQ in VB.NET, something like this:
dim strId as String = "1,2,3,5,"
dim myList = from objmylist where objmylist.id in (strId)
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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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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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Jun 7, 2012
On my view there is a datatable holding a collection of ServerRow and 4 textboxes (Hostname, OS, Location, Zone). When the user types into any of the 4 boxes I want to immediately filter this list. I have this code setup and ready to go that on the set method of each textbox property I call the filter method.
Now onto the problem: if I have 4 criteria that means I have 2 to the power of 4 different scenarios. What I would like to do is write a linq statement with all of these scenarios dealt with such that if any of the properties are NullOrEmpty they will not be used in the Where clause and on the flip side if there is a value the corresponding field will be searched with a Contains.
Example
AvailableCis = New ObservableCollection(Of ServerRow)
(_CiData.Where(Function(ci) ci.OS.ToUpper
.Equals(_selectedOS.ToUpper) AndAlso
ci.HostName.ToUpper.Contains(_ciNameFilterText.ToUpper))
.OrderBy(Function(a) a.CiName))
This example shows how it works with 2 criteria and both of those criteria are set.
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Apr 24, 2009
I am binding a Winforms Grid to an entity. (For reasons I won't go into here it must be bound to the entity, not the result a query) The code is as follows:
grid.DataSource = myEntities.entityName.Where("it.field = " & field)
It works, but it obviously isn't strongly typed. Is there a way to define the Where clause of an entity using a strongly typed notation?
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Jan 18, 2012
In my ASP.Net Web-Application, I'm getting this error: Conversion from type 'DBNull' to type 'Boolean' is not valid.
[Code]...
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Dec 13, 2011
I am teaching myself vb.net with visual studio 2010 and i have ran into a wall. I have a datagrid on my form that shows all of my customers that are in the dataset that was created in access 07. I have a search bar and check boxes to select which column name to search in. Whenever I search it throws up a strong typing exception,
System.Data.StrongTypingException was unhandled by user code
Message=The value for column 'PickupTime' in table 'CustomerRouteTable' is DBNull.
Source=EXBSTESTDatabase
[Code]....
I think this means that there is nothing in the field, but this is a field that nothing should be in. If i comment the throw exception out it moves on to the next one that has nothing in the field. I tried just putting 0's in all of them but it still gives the same exception.
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Nov 9, 2011
I am receiving this error on this line
ctl.Value = CType(Me.Value, DateTime)
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Jan 19, 2012
I have been having an error that DBNull cannot be returned as a String and after hunting around I came up with the folowing but have had no sucess. it is very inportant that this code can handle DBNull as it will encounter this often.
[Code]...
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Mar 10, 2010
Dim k as nullable(of double)I am INSERTING a rec in database containing K (sometimes it has some value otherwise a null) It works ok.But when i UPDATE a rec and assign a field the value of k and when k is NULL
it gives me an error that you cannot assign a NULL , you should use DBNULL.But i think DBNULL.value can only be assigned to an object not to double.
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Nov 12, 2009
I need to make something like :
if isdbnull(value) or value = something then
'do something
else
[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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Dec 21, 2011
I'm writing a program for my friend as a gift. He's a movie lover, and has this Excel spreadsheet with all the movies he's watched in it. I converted the spreadsheet to an Access database,then used that database in my program. I've been going by the example in my textbook (Programming with Microsoft Visual Basic by Diane Zak), and everything been working until I put in a "Find Movie Title" button. I want to be able to search the column "Movie Title" for a title input by the user (whether it's the whole title or just a few characters)Here's the code:
Private
Sub btnFindTitle_Click(ByVal
sender As
Object,[code].....
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Jan 13, 2012
Why does the following code: A = not IsDBNull(CurRow("BuyBook")) AndAlso CType(CurRow("BuyBook"), string) = "Yes" results in the following error:
Conversion from type 'DBNull' to type 'String' is not valid.
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Nov 17, 2010
I am writing a program that pulls data from a database.For each table that I pull data from, I write a series of If Than Else Statments to catch any null values and assign Nothing so as not to throw an exception.Is there a way to check against a DBNull value without writing an If THan Else Statment for each column I am pulling from the database?
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Feb 10, 2010
I have simple app code:
Dim sw As New StreamWriter(FileName, False, System.Text.Encoding.GetEncoding(Encoding))
Dim adapterPositions As New MyDatabase1DataSetTableAdapters.PositionsTableAdapter
[Code]....
How I can check column is DBNull or not?
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Apr 17, 2009
Is it possible to converty a type System.DBNULL to a string type?
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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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Nov 24, 2009
this code i pick from grauva khanna... it working..but for one coulmn only.. my question is ..how to manipulate every column with dbnull.value
'If TextBox1.Text.Trim = "" And TextBox2.Text.Trim = "" And TextBox3.Text.Trim = "" And TextBox4.Text.Trim = "" Then
'DT.Rows.Add(DBNull.Value, DBNull.Value, DBNull.Value, DBNull.Value)
[Code].....
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Jun 6, 2011
I have a piece of code im working on and is stuck on Select Sum statement which keeps returning a Conversion from type DBNull to type Decimal is invalid. Below is the code and Im working with a Access Database. Everything works good if the Batch Number exists and its when the Batch Number does not exist.
[Code]...
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Dec 14, 2009
I have a form with some textboxes in it. Not all the boxes are mandatory fields. I also have a store procedure that saves the records to the DB. when I try to save a record, I get an error PLS-00306. I am passing the required number of parameters to the sp. When I populate all the fields, the record is saved but NOT when some fields are left blank.
If txtInvoiceRef.Text = Nothing Then
strSQL.Parameters.Add(New OracleParameter("varInvoiceID", OracleDbType.Varchar2, 50, ParameterDirection.Input)).Value = System.DBNull.Value
ElseIf txtPaymentDate.Text = Nothing Then
strSQL.Parameters.Add(New OracleParameter("varPaymentDate", OracleDbType.Date,
[Code] .....
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Jun 30, 2010
I have a dgv with some checkbox columns. When I load data in the dgv, and I want to check in the cellcontent_click event, whether an another cell value (this is a checkbox cell too) is true or false, I get the error that the operator = is not defined for
dbnull value and for boolean. F.e.:
If
dgvegyenijogok.Rows(e.RowIndex).Cells(3).Value = True
And
dgvegyenijogok.Rows(e.RowIndex).Cells(4).Value = True
And[code]......
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Oct 12, 2011
how to set a field in a dataset table back to <DBNULL>?
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Jan 4, 2012
This code is supposed to return all the records where the month component of the DateCreated is equal to the specified MonthIssued value. The problem is, if DateCreated is DBNull I will get a runtime exception which requires the extra If ternary operator. Any way around this / will this cause a performance hit the code is actually executed?
[code]...
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