How can i return null values in if statement above. This statement is not working if condtion is false its retruning me 0 value even if condition is false
dim d as nullable(0f Decimal)
d=(if(_dr("value") isnot dbnull.value,Convert.toDecimal((_dr("value")),Nothing)
We had a Nullable object must have a value error today on this line of code:list = From x In Me Where x.FooDate.HasValue AndAlso x.FooDate.Value.Date >= barDate
Funny thing is that I feel sure this used to work fine (and there has always been a sprinkling of null values in the underlying data). And logically it looks fine to me. The check for HasValue and the AndAlso look as if they're going to shield us from any Null danger.But it seems suddenly they're not. Am I missing something?OK, we can correct it to this, which eliminates the error:
list = From x In Me Where If(x.FooDate.HasValue, x.FooDate.Value.Date >= barDate,False)
But this looks to me less readable. In simplifying the above code to shorten the line I left out a crucial chunk of the code. The original problem should have read something like:
list = From x In Me Where x.FooDate.HasValue AndAlso x.FooDate.Value.Date >= fromDate And x.FooDate.Value.Date <= toDate
Because of the rules of shortcircuiting and operator precedence (as outlined in an answer to a long ago question of my own) I needed to add brackets round the second part of the instruction in order to stop LINQ evaluating the second x.FooDate.Value.Date:
list = From x In Me Where x.FooDate.HasValue AndAlso (x.FooDate.Value.Date >= fromDate and x.FooDate.Value.Date <= toDate) LINQ really does obey AndAlso and force me to look more closely at the original problem.
Apparently this used to be a way in VB6 and VBA to short circuit and execute the first true case:
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I want to create a custom date type. I want to allow null values, and return a string to the user if no date if specified.
View 13 RepliesI have a dataset and I am referencing items in it like this:MainForm.DataSet1.Tables("JobsTable").Rows(1).Item("JobName")
View 5 Replies[code] Error4'Char' values cannot be converted to 'Short'. Use 'Microsoft.VisualBasic.AscW' to interpret a character as a Unicode value or 'Microsoft. VisualBasic.Val' to interpret it as a digit.
View 1 RepliesReturn statement which is true in an if statement
View 3 RepliesI cant get this SQL statement to insert any of the values in the form to add to the database
sql
sql = "INSERT INTO prevresults (ExamDate, ExamTime, CorrectAnswers, PassPercentage) VALUES (date.now, time.now, rightanswers, percentage.text)"
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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].....
I am currently using a sql data reader (in vb.net) to extract an article object via a stored proc from a SQL Server 2008 database. Part of this object includes the two properties shown below:
theArticle.Truthfulness = ((myReader.GetInt32(myReader.GetOrdinal("Truthfulness"))))
theArticle.Relevance = ((myReader.GetInt32(myReader.GetOrdinal("Relevance"))))
My problem is that the Truthfulness and Relevance may return a null value and this is causing the function to fall over.I think I understand why. I am asking for an integer value (getin32) and because null is returned it fails.How do I accommodate the null value from the database so it does not fall over?
I'm having trouble figuring out what to do with the bolded part, when there are no nodes to return.If there are no image tags inside the <images> tag, i get an "Object reference is not set to an instance of an object".I have been searching and searching for an answer but can't find one.
Dim orders = From o In xmlLinq.Descendants("order")
Select New With { _
.orderID = o.Attribute("id").Value, _
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i am retrieving data using data reader. Whenever a null value fetches from the column, the compiler encountering an error. The error occurs when column value contains NULL. I am using Visual Basic 2005.
Please look at the following error which is in red color:
DEVNA11.Checked = IIf(IsDBNull(dr("dev_serv_desc_final_na")), 0, dr("dev_serv_desc_final_na"))
txtPlanServDesFinal.Text = IIf(IsDate(dr("dev_serv_desc_final_planned")), Format(dr("dev_serv_desc_final_planned"), "dd/MM/yyy"), dr("dev_serv_desc_final_planned"))
System.ArgumentException: Argument 'Expression' is not a valid value.
Take the below example. I would expect the IsInterned method to return null, because this string can't possibly be in the intern pool having started up the test app for the first time? I would also expect, that if I did something like string.intern("this112233StringCan'tPossiblyBeInTheInternPool!£$%") first, then this would legitimately be returned by IsInterned from the pool. I've also done the same in c# and the behaviour is the same.
Whenever I use strings in code, I tend to do something like textbox.text = string.intern("someValue") etc or if (textbox.text = "someValue") etc. Infact, whever strings are being used, I've gotten in to the habbit of using string.intern. Is this a bad habbit rather than using constants or the resources file?
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Now that I've switched over to parameterized queries, everything is great except along with handling all the special characters that would otherwise disrupt an all text SQL stament, it's handling the word NULL. My code basically does this for every variable used in the entire SQL statement:
If strCallName = "" Then
strCallName = "NULL"
End If
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and that worked great for my old all text ones because leaving the word NULL out of single quotes would tell it yeah, that's actually null and pass it a true null value. Now with parameterized ones, it's literally passing it the word NULL I tried just leaving the string empty but then when I try to execute the command, it says that the parameter cannot be a zero length string. So how do you give a null value to a a parameterized query and make it actually send that to the database in the statement? Would strCallName = vbNull work or would it still say it's a zero length string?
I am still a newbie with VB. If I return a number the if statement works fine, with opening the new form and updating it as needed. Id the if statement returns a Null from the database it crashes.
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I want to retrieve total value from sales table in sqlcommand object. Below is my sample code.I will get error if there was no data in the tabel that matched my query saying that null could not be converted into decimal.
I would not get error if there was data that matched my query and returned the total value in tmpSales variable.My question is what is the best way to deal with this situation?
Dim CmdTmp As System.Data.SqlClient.SqlCommand
Dim tmpSales As Decimal
CmdSales = New System.Data.SqlClient.SqlCommand("SELECT SUM(Total) FROM Sales WHERE Date>= '1 Jan 2011' And Date<= '30 Jan 2011", ConDB)tmpSales = CmdSales.ExecuteScalar
I have a datetimepicker and combobox on my form. If a user does not change the date on dtpicker or does not change text on combo box, these controls return null value, and the save operation fails. The controls are bound to data in a database.
View 1 RepliesMy code seems to behave a way I don't understand. Sometimes it returns null as expected and sometimes it returns a value when its supposed to be null. How can someone explain this? Here is the code that selects from access and displays the result in a messagebox:
cmd5.Connection = cnn
cmd5.CommandText = "SELECT receipt_num " & _
"FROM brought_coffee, farmer where crop_year= " & yr & " and " & _
"brought_date=#" & dtt & "# and farmer_centre='" & ctr & _
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Am I just being blind or does this If statement genuinely not do what it's meant to.[code]This displays the message box even though textSample is one of the letters. In my eyes that If statement should see that textSample is one of those letters and skip it, whereas if it was Z it would "Not" be equal to any of those and would therefore show the message box.
View 6 RepliesI have the following piece of code that I am using to try and rip a csv file and turn it into a datatable. My problem is that the debugger never makes it to the return statement. Everything is appending to the datatable correctly, so I know that part works. Any idea's on what I can do to trouble shoot this further. Also, if you know of a simpler way to turn a import a csv file to a datatable I'd be very interested in learning about it.[code]..
It say that the Object reference is not set to an instance of an object. What's weird though is that it works through the whole data table fine. Could it be that the while loop is not terminating at the end of the file?
I know normaly you have to use Return before "End Function", but now the Return is in the Try and Do statement and I can't find a way to variable the Return.[code]...
View 7 RepliesI am a little confused about the use of a return statement in a function. If I understand correctly the return statement returns a value but where? Where is the value being returned to?
View 1 RepliesI have the following query that I use to create a new record in a database. If I leave any field on the form blank, for example, it throws the error "Memo.Lastname" cannot be a zero length string. Other than that the query executes appropriately.
Private Sub cmdSaveMemo_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles cmdSaveMemo.Click
If Len(Me.txtMemoID.Text) <> 0 Then
Memo.SaveMemo
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In every date field I have, I cannot update it if it is null. For instance, I have the following query and it will throw an error if the date fields are Null or zero lengths. Any ideas? I try and parse and get the following error: String was not recognized as a valid DateTime. if i don't, it throws a null error.[code]
View 7 RepliesI have 2 functions that need to work together.1 function is to generate a chart number. The other function is to search via SQL to see if the chart number exists. if the chart number doesn't exist then i need function 2 to return a boolean value so function one can generate a new chart number example code: [code] Now i know that i am probably using the incorrect sql statement, my main issue is that i dont know how return available back to the function.
View 1 RepliesI just want to know whether there is any method to return from a goto statement.
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Dim SQLData As New System.Data.SqlClient.SqlConnection(ConfigurationManager.ConnectionStrings("FixedLineProvisioningConnectionString").ToString())
Dim cmdSelect As New System.Data.SqlClient.SqlCommand("INSERT INTO tblTotalComms_custinfo SET nt_username=@nt_username; SELECT @ID=SCOPE_IDENTITY()", SQLData)
[Code] .....
I want to return the value @ID from the insert statement.
I am developing a code to open up a .dbf file and append data to a access database.Here is my code for opening the .dbf file.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim constr As String = "Provider=VFPOLEDB.1;Data Source=F:JUNO4.dbf;Persist Security Info=False;"
Dim con = New OleDbConnection(constr)
Dim da = New OleDbDataAdapter("Select UNIQUE_ID FROM JUNO4", con)
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this code gives an empty datagrid.
1. I would like to know why a Return statement is needed in the function in the first set of code, but not in the second(even though it still works with the Return statement). The functions are called the same way, so what is the difference?2. Why in the second code, the variable FutureValue is allowed to have the same name as the function? But when, in the first set of code, I try to rename the variable "discountPercent1"(in the function) to the function name "SetDiscountPercent", VB 2008 Epress gives the error message "The name conflicts with an existing symbol with the same name"?
Public Class frmInvoiceTotal
Private Sub btnCalculate_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnCalculate.Click
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I have this simple-minded query:
select a.str_number+' '+a.str_name+' '+a.str_suffix+' '+a.str_apt AS addr from mytable
This query works as long as none of the concatenated values are not NULL. If any is null, the address does not show.
I tried this:
select IsNULL(a.str_number+' '+a.str_name+' '+a.str_suffix+' '+a.str_apt AS addr,'') from table
What I would like to accomplish is to replace NULL with empty space if the value is null but I still get no values.
