I have a if then else if statement to check the value of a combo box then assign a variable depending on the combo box value. The problem is that the variable in the if then statement never gets assigned and then when I call it later in the program out side the conditional statement I get this warning. Variable 'srtype' is used before it has been assigned a value. A null reference exception could result at runtime. here is the code.
error
Dim srval As String
Dim type As String
Dim srtype As String
Say that i have the following code that parse about 20k records from the DB.
Code #1
vb.net While reader.Read() list.Add(If(Integer.TryParse(reader(0).ToString, 0), Integer.Parse(reader(0).ToString), 0)) End While
And then another code which does the very same thing but it seems to be a little cleaner.
Code #2
vb.net While reader.Read() Dim storeowner As Integer = 0 Integer.TryParse(reader(0).ToString, storeowner) list.Add(storeowner) End While
This is what i am confused about; does the compiler creates a new variable automatically when i use the if statement without strictly declared variable? What approach is better in sense of performance?
here is a With...End With question. With variable As Type = value .property = value1 'I can access its properties Function f(.) 'syntax error, but how can I access the variable itself? End With
I need to assign a varible in a while clause. I.e., i would do it in php like this: while (!is_bool($char=$this->getChar()) in every loop, the function would assign $char a value, the is_bool function would test it, and the code INSIDE the while clause would have access to that $char.
I have a simple vb script which extracts some data from our accounting software to a text file. It works fine when I do not use a variable in my select statment as follows:
xselect = "SELECT SourceJournal,JournalRegisterNo, PostingDate, PostingComment,UserCreatedKey FROM GL_DetailPosting
I want to pass/use a variable inside a sql statement. The code is the following:
Dim i As Integer = 2 Using Command As New SqlCommand("SELECT Comment FROM Params where id=' " & i & "' ", objConnection)
I tried to pass the i variable by using the ' " & i & " ' but it doesn't work (I am getting an error like - Conversion from type 'DBNull' to type 'String' is not valid. )
I have noticed in VB.Net that most Dim statements also include an assignment. Eg:Dim myvar As String = "Hello World"As this wasn't possible in VB6 I have always done the following:
OK So I know WHY I am having the error I am getting. I don't know HOW to fix it. Basically, if the user doesn't have a certain permission, I need to join another table. But .NET is so picky I can't just make two different queries in an IF statement and then use it outside of the if statement. I can think of some ugly work arounds for this, but I would rather not. I am fairly new to .NET I know just enough to be dangerous.
[Code]...
because of this: Dim l As IEnumerable(Of Company) its not just IEnumerable of a Company, its got the source in it. I have to explicitly select source to use it in my datagrid. Can I make Dim l something that will make it stop complaining?
I'm relatively new to VB. I want to perform a SELECT statement that uses a variable to return a value, example; mysql> SELECT room_description FROM room_descriptions WHERE current_room = 'someVariable'; And display the result in a TextBox i.e. TextBox.text = someVariable. So how do I perform a query from VB that passes a variable? How do I assign the result to a variable?
In my programming task I've gone down a dark alley and wished I hadn't, but there is no turning back now.
I'm building up a SQL statement where the table name, column name and id value are retrieved from query string parameters i.e. ("SELECT [{0}] FROM [{1}] WHERE [Id] = {2};", c, t, id)
But it isn't as bad as it looks, I'm protected: Only authenticated users (i.e. signed in users) can execute the Page_Load I'm checking that both the table and the column exists beforehand (using GetSchema etc.)I'm checking that the Id is an integer beforehand All my tables have Id columns The database connection is reasonably secure
As you can see from the code below there is a lot of repeated code. I want to move that code outside the if statement as it's performed for each if, but the Dim employees variable I'm declaring is causing my issues. I don't know how to declare the variable outside the if statement as it's a linq-to-sql query, so I can later define it within the if statement. I can't access employees outside the if statement, so I can't just put the repeating code outside the if statement.
Private Sub btnFindEmployee_Click(sender As System.Object, e As System.EventArgs) Handles btnFindEmployee.Click If chkSrcEmpID.Checked = True Then
I have an application that contains both test code and production code. The test code points to the test files on the local machine while production is located on the server. I comment out the production code when testing. To save some time I figured I would create a Global Variable integer called pTest and encase the test and production code in a Case statement so that if I set pTest=1 then the test code will run and if pTest=0 then production code will run.
Dim d as Date = DateSerial(Year(rptDate), Month(rptDate), 1 - 1) Dim conn as OleDbConnection = new OleDbConnection(connStr) Dim cm as OleDbCommand = new OleDbCommand()
[code]....
I know that d is the same date as the one in SQL server, specifically 3/31/2011 12:00:00 AM.
As you can see below in the code the " & tblName & " will work fine but instead of using the BankName (which the user cannot change because it is in the code) I would like to do the same as I did with the Table name and use a variable that gets its name from an excel spreadsheet rather that an actual name hard coded in a VBA module. I would like the variable field name entered in the Excel Spreadsheet by the user just like the table name is filled in by the user. The problem is getting the ADO SQL string ( cmd.CommandText = "ALTER TABLE " & tblName & " Add Column BankName Char(25)" ) to recognize that the value in the Variable " & fldName & " is the field name to be used.
Sub AddFieldToAccess() Dim cnn As ADODB.Connection Dim cmd As ADODB.Command
[code]....
'If I do this I end up with a field named BankName what I need is the name in the variable " & fldName & "
I am getting the error:"Range variable 'sender' hides a variable in an enclosing block or a range variable previously defined in the query expression."for this
Imports System.Data.SqlClient Imports System.Linq Public Class Form1
[code]....
I can select any other item from the table without the error. "sender" has the same properties as "receiver" in the SQL table.
I was convinced that If <expression> Then <statement [:statement]> Else [statements] in concrete form of If a = b Then SayHello() Else SayBye() End has sense. I read article on msdn on If-then-else, but I forgot why I was reading, so I concluded, that snippet above means this
If a = b Then HelloIsSaid : IsNotEnded Else ByeIsSaid : IsEnded But I have tested it now, and I see, that Else without statement is nothing more than decoration. It would be pretty good if it had function I described. Do you think its good request? Or do you know any circumstance where this Else has some function?
I want to put it (the select count statement) in this LINQ statement so I can get the sales count in my linq statement: Dim TheLeads = (From L In DB.Leads Where L.IsDeleted = False Select L).ToList() Is this possible to do in LINQ?
add an if statement and an exit statement to my do loop that exits when my future value (FV) is greater than 1000, then to change the exit statement to a continue statement so my loop will continue even though my fv is greater then 1000, point is to get this to run even though my if statement doesnt do anything. problem something wrong in my code and an exception error (xception of type 'System.OverflowException' occurred in mscorlib.dll)
so can someone show me where or why I have an error is, what am I overthinking now! I could use a hint, OMG i could use a tutor for that matter
I'm writing something that will examine a function and rewrite that function in another language so basically if inside my function F1, i have this line of code var x=a.b(1) how do i break up the function body into symbols or "tokens"?I've searched around and thought that stuff in System.Reflection.MethodInfo.GetMethodBody would do the trick however that class doesn't seem to be able to have the capabilities to do what i want..dit 2:basically what I'm trying to do is to write a program in c#/vb and when i hit F5 a serializer function will (use reflection and) take the entire program (all the classes in that program) and serialize it into a single javascript file. of course javascript doesn't have the .net library so basically the C#/VB program will limit its use of classes to the .js library (which is a library written in c#/vb emulating the framework of javascript objects)
how to use them then before, but am still a little confused with a few aspects. Here goes:
1.) Lets say you have a method that checks for a certain condition(s) and if it fails Throws an exception. Does it have to be in a try/catch block? Meaning can the "Throw" statement exist in a block with no try/catch statement?
2.) Now lets say we have a method that has a try catch block and in it there is a throw statement. When the throw statement is executed does it first try to find an appropriate catch block in the same method or does it immediately go back to the calling method without looking at the catch statements in the current method where the exception was thrown?
3.) I created a custom exception class that inherits from ApplicationException. Next I created a method which has a catch block that catches this type of exception and does some action. Is the System(i.e CLR) smart enough to throw an exception of this type, or does it only throw exceptions from SystemException?
4.) I know that some people are more liberal in their use of exceptions and others use it more sparingly when truly strange stuff happen like the DB going down. I am writing code where I am getting some info back from the database, converting it and then storing it. Sometimes there might be data that comes back from the database and other times the field is empty and the Null value comes back. Therefore in the instances where Null comes back from the database I should not convert the value to anything, since I will get an error. What should I do in this situation? Should I let the CLR throw the exception when it goes to convert the Null value or should I check for the Null value and if it exists not convert?
5.) In general when I throw exceptions, is it sensible to only throw exceptions of the type Application Exception or are there instances where the programmer throws exceptions of the type SystemException?
I'm building a listview search feature in my app. (See the code below). It works really well, except if you search "T" then the code removes all items, if you search "t" then it removes every item except for those starting with "t". Is there any way to make a 'like' statement, or use some kind of wildcard to make the statement not case sensitive?
For Each itm As ListViewItem In ListView2.Items If itm.Text Like TextBox1.Text & "*" Or itm.SubItems.Item(1).Text Like TextBox1.Text & "*" Then Else
