I need to check if a value from a date column is equal to null. I can't find how to do it.
Wat I got now is:
if ds.tblBooking(row).CancelledOn.compareTo(dbnull.value) = true then
But this doesn't seem to work, I think it's because I'm using a strongly typed database.
I keep getting the error "Object reference not set to an instance of an Object" on the below highlighted line of code and I understand why. It's because I'm checking for something that hasn't even been initialized yet. My question is, what's the best way to check a DataTables row count without getting that error before refilling it?
If Not ds.Tables("tblNotes").Rows(0).IsNull(0) Then
ds.Tables("tblNotes").Rows.Clear()
End If
adp.Fill(ds, "tblNotes")
I have an ASP.NET application that crashes when a null date value is returned.
The code line is:
excelWorksheet.Cells("A" & xlRowCounter).Value = IIf(IsDBNull(dRow("sysdate")), "", Format(dRow("sysdate"), "MM/dd/yyyy"))
Error message:
ERROR: System.ArgumentException: Argument 'Expression' is not a valid value.
How would I check for a null date, and replace it with "" in my app ?
I have a DataSet where I need to filter the collection where one of the date columns is not null.
How do you term this in LINQ?
This is what I have so far but there is a compiler error on the w.CompletedDate field in the Where clause.
Dim completed = From ins In InspectionDataset.Inspection.AsEnumerable _
Where (Function(w) w.CompletedDate IsNot Nothing) _
Order By ins.Field(Of DateTime)("UpdatedDate")
I have also tried it the below way but the compiler will not allow the DBNull comparison.
Dim completed = From ins In Inspection.AsEnumerable _
Where ins.Field(Of DateTime)("CompletedDate") <> DBNull.Value _
Order By ins.Field(Of DateTime)("UpdatedDate")
I have a DataGridView1 populated by sql searches. On the rare occasion that nothing is returned, my app cannot make use of data so I'm trying to check for null values. My code below is not correct because IsDBNull is not a member of the of the DataGridView1.
If DataGridView1.SelectedRows(0).IsDBNull Then
MsgBox("Nothing to display")
Exit Sub
End If
I have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
[Code]....
Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:
If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?
In the following code, a Date variable is declared but not set to anything:
Dim myDate As Date
What's the proper method of checking if the Date variable is "new" and not set to anything?
For example, getting the lowest date value from an array of dates:
Dim dtMostRecent As Date
For i As Intger = 0 To myDateArray.Count - 1
If myDateArray(i) < dtMostRecent Then dtMostRecent = myDateArray(i)
Next
In the code above, I need a way to check first if dtMostRecent is unassigned, in which case just give it the first value, after which it can be compared with subsequent values. How to check if a Date variable is unassigned.
I have the following
If Trim(txtConfirmationDate.Text) <> "" Then
sqlinsert2.Parameters.AddWithValue("@CONFIRMDATE", CDate(txtConfirmationDate.Text))
Else
sqlinsert2.Parameters.AddWithValue("@CONFIRMDATE", VB.vbNull)
End If
Unfortunately, it writes "01/01/1900" to the database. How do I get it to just leave the field as NULL?
How can I get this to happen? I googled around and it seems setting the CUSTOM FORMAT to " " when the field is null will work but not for a BOUND datetimepicker.
View 12 RepliesI'm fairly new to ASP.NET & VB.I've been asked to take an existing textbox that is automatically filled with the current date and allow the user to either add a "+" or "-" and a number or a spcific number and convert that into a date.I underdstand the basic concept on how to do this, but I'm running into some problems using the proper commands in order for this to work.The Textbox is called txtDate.What I've tried to do is this:
If txtDate = '+' Or '-' Then
DateAdd("d", txtDate, today)
End If
Here is what the whole thing looks like:
Protected
Sub
DateEnter_Click(ByVal
sender As[code].....
I have several records in a database that have Start and End Dates
09/15/2011 - 09/30/2011
10/15/2011 - 10/22/2011
11/01/2011 - 11/15/2011
When user stores a record, I need to make sure dates don't overlap.My simple code checks date ranges within a specific record (e.g. user enters 9/16/2011 or 10/21/2011, I throw an exception.)But, on the slim chance a user gets creative (e.g. 10/14/2011 - 10/23/2011 or even 10/14/2011 to 11/16/2011), now they have circumvented my check.BTW, the user could enter 10/14/2011 to 10/23/2011 if they were editing the record that contained values 10/15/2011 - 10/22/2011.So, I'm trying to solve this riddle with a linq query. However, what I have isn't working exactly right.
UPDATE Nevermind about code not working. While trying to provide an example to expand on Miika's repsonse, I found my answer. So, giving credit to Miika for pointing me in the right direction and posting my working code below:
Here's my code:
Private Sub CheckForOverlap(myMonth As Messages.MyMonth)
Dim am As New MyMonth()
Dim amCollection As Messages.MyMonthCollection
[code]....
checking im my textbox contains null valuefor example i have ten textbox how do i know if a textbox has no text in it?then gotfocus to that specific textbox?
View 3 RepliesI'm using Visual Basic .NET to work with a USB HID device.Most of the time, I can receive data from it perfectly... but one out of every thousand transfers or so, my code will think it has received data when it actually hasn't.The device writes to an array of bytes. I wanted to check to see if the received packet is empty, by doing something like this:
If myDevice.dataPacket(1) <> Nothing then
myDevice.rxDataReady = False
[code].....
ve a simple vb code similar to the below,
Function getvalue (ByVal Val as double) As string
Dim Num as Integer
Dim Prd as double
[code].....
Is there anyway to check for a null here before it reaches this part of the code? tmpLabelData(0) = m_node.Item("CONTAINER_NAME").InnerText. Some XML has it while others do not. I cant seem to find a nice way to handle a null on these?
View 1 RepliesI'm querying a SQL DB and sometimes the result is Null, so I thought I would test this but my code results in an error "Data is Null. This method or property cannot be called on Null values."
Here is a snipet of my code:
For i = 5 To 6
cmd = New MySqlCommand(query2t & i, db)
rdr = cmd.ExecuteReader()
rdr.Read()
If Not IsDBNull(rdr.GetUInt32(0)) Then
[Code] ......
I have some code that is meant to check the length of the values in the text boxes, and if any of the boxes has no content the length of the string is 0 (or null). Here is the code:
If (Len(Form_MainScreen.Ctl48.Value) Or Len(Form_MainScreen.Ctl49.Value) Or _
Len(Form_MainScreen.Ctl50.Value) Or Len(Form_MainScreen.Ctl51.Value) Or _
[code]....
When one string is blank, the length check becomes "null" and so does the whole statement.But if the length checks are all not null, the if statement becomes a "1" and then procedes to execute the Do X procedure again.
I'm working with a database application and i want to check if there is a null value in a specific column but it works only when its not null but if its null it throws an exception automatically. I tried to change the null value property of this column but I'm not able it shows a message that its not a valid property. I tried to change the source code in the code editor but it changes back automatically. Is there a way that I can work around this?
View 5 RepliesI am trying to write a generic function that will check each database parameter to see if it is null, and if so, return DBNull; if not, return the object.So here is my function:
Public Shared Function CheckForNull(ByVal obj As Object) As Object
If obj <> Nothing Then Return obj Else Return DBNull.Value
End Function
[code].....
I constantly find myself having to do code similar to the following.[code]Is there anyway to check for both on a single line? When i'm checking a condition for a great number of answers, I sometimes end up with conditionals 6-sets deep. If i check for null first, an error still pops up, even though VB shouldn't check since the first condition failed. i.e.[code]
View 8 Replieshow to check null excel worksheet?
View 2 RepliesI'm implementing a State Machine in WF 4.0. In some transitions, I have added a condition where I check that some variables have the expected values. The variables are enums and booleans, and everything is fine.
However, now I tried to evaluate when a property is null. I have and argument in my workflow, let's say, 'MyArgument'. In a transition, I try to put a condition like 'MyArgument.MyProperty = Nothing'. I never developed in VB.NET, I don't know if I'm missing something here...
VS2010 gives the following error: "Error 4 Compiler error(s) encountered processing expression "MyArg.MyProp = Nothing".
Operator '=' is not defined for types 'XXXX' and 'XXXX'
The type names are exactly the same, and I have debugged VS2010 to ensure that my assembly is not loaded from 2 different locations.
How can I check if the property is null or not?
BTW, I'm using VS2010 SP 1, with .NET Platform Update 1 installed, on W7 64 bits.
I am trying to implement a function for my SSRS report which will return a color value depending on the values of three dates.
[Code]...
I am using following code in rowdatabound fn.
Protected Sub gvwMileStone_RowDataBound(ByVal sender As System.Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs)
[code]...
ddlEProjectLevels is dropdownlist in edititemtemplate.Whwn i click edit in 1st row ddlEProjectLevels gets loaded with data from database.But in 2nd row dropdownlist does not contain values.Again in 3rd it gets loaded from db.Means in alternate rows,when i click edit dropdownlist(ddlEProjectLevels) doesnot load values.Can anybody help?
I need to check my field in format ddMMyyyy(ex 12/03/1990) whether in interval of two dates that user picks from two date picker controls. Two date pickers are in custom format dd/MM. It does not matter for me if its between particular years. I need just to know if given Birthday belongs to interval taken from screen. Each datepicker gives values dd/mm/yyyy. I do not know how to check it. For example:Given date 12/03/1990 . User select two values from screen: From 01/01/1950 Upto 30/04/1949(or 1990, or 2000)
Result should be True.Because 12 march is between 01 Januar and 30 April.
How do i check if the dataset is empty? I wrote the following code:
[Code]...
I am stuck with the following code (below). Basically, I have two data sources; a flat text file and a dataset. I am trying to put the primary key from the flat file into a simple variable, and the PK from the dataset into an array. I then use a 'for each' statement to compare the PK from the text file to the PK in the array (from the dataset). If they match, the "isValid" variable is supposed to equal 'false'.
Unfortunately, this is not working. the isValid is always true, which I know is not the case, and then I get a SQL error warning of primary key violation. I'm a bit tired, and not seeing it. Here's the code;
For x = 0 To XLength - 1
Dim SessionID As Integer = Integer.Parse(FileData(x, 0))
Dim IsValid As Boolean = True
[Code].....
I am using the DataSet to test for data errors on a DataGridView (to give the user feedback before they save changes back to the database). RowChanging event has the code at the bottom and this manages error messages on the DGV via an ErrorProvider. I want to add something to this code that esnures there are no duplicate rows (it's a 2 column table and one of those is the autoincrement PK). However I cannot work out how to do this and since the column in the database is set to Indexed (No Duplicates) it will throw an Ole error if I don't handle it, I could manage it in a Try block around TableAdapter.Adapter.Update but would prefer not to add needless round trips to the DB when it really ought to be simple to do it in the code (and preferably in the DataSet, not the form).
I found the following code (Forum Post) and try as I might I can't make it work since I can't get access to a DataTable within the RowChanging event that allows me to run DataTable.Rows.Find().
Dim expression as String
Dim matchingRow as DataRow
matchingRow = Mytable.Rows.Find(expression)
In my case:Mytable would be some kind of reference to the table / dataset etc.
'expression' would be e.Row.compclass.ToString
* a reference to the database table the form works with (bearing in mind that this code is in the DataSet not in the form). I've tried properties/methods of the DataSet itself; creating a new DataTable and linking it to the DataSet Table (or DB Table); creating
a new DataTable and loading it with the table contents - Searching MSDN and the forums hasn't popped anything up yet.I'm currently experimenting around this code:
Dim strCompClass As String = e.Row.compclass.ToString
strCompClass.Trim()
Dim foundRow As DataRow = ???.Rows.Find(strCompClass)
[code]....
This is the current code in the RowChanging event. The new code would be inserted after the last End If in the code below.
Private Sub ref_compclassDataTable_ref_compclassRowChanging(ByVal sender As System.Object, ByVal e As ref_compclassRowChangeEvent) Handles Me.ref_compclassRowChanging
If e.Row.HasErrors Then
[code]....
Public Sub checkemail()
sqlcheckemail = "select Email from WEBUSER where Email='" + TBEmail.Text + "'"
Dim dscheckemail As New DataSet
[Code]....
if u see the one that i've commented is the one i already googled at tested...so now if the email address exist in the db..everything works wonderful..but if it doesn't exist the code should process the one that does not satisfy the first if statement...but now i'm getting the result as "There is something" eventhough the email does not exist in the db...
I have the following code in my application. When it is executed it brings out a null value at times, where i am sure there should be a value returned. I have checked by running the sql statement in the database and it returns the correct value. What could be wrong with my code? [Code]
View 6 Replies