How To Convert Null Value To String
May 23, 2010
foreach (PropertyInfo PropertyItem in this.GetType().GetProperties()) {
PropertyItem.SetValue(this, objDataTable.Rows[0][PropertyItem.Name.ToString()], null);
}
In one of the loops i get this exceptional error:
Object of type 'System.DBNull' cannot be converted to type 'System.String'.
The error occurs because one of the fields in the database has no value (null), so the string property could not handle it. How can I convert this null to string? I'm trying to avoid checking on every loop is current value is null or not.
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Dec 16, 2009
Is there any way to convert null terminated string to normal string.I mean I can easily make a program to find the location of vbnull but there has to be a built in function for that.
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Mar 30, 2010
I tried this
Dim value As
String
Dim returnValue As
[code]....
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Jun 7, 2011
i am working in windows appl vb.net 08. And i am working in Access DataBase.I have one Table Called "Person" . In this "Person" Table one Column Name Called "OtherName". In this Column binded in one of the Combobox in a Form.But the Problem is "OtherName" Column having the Null Values.Before i bind this Column to Combobox i want to convert this NULL Values to String. Why i need the values in STRING means , In my code i using this Combobox as a filter in SQL Query.If i didn`t change the Null Value to STRING , The Combobox SelectedText or SelectedValue is Showing Nothing. So i am not able to get the Record.
Whn i write a Sql Query to Combobox and apply filter in WHERE statement like Combobox.Selectedtext or Combobox.SelectedValue In "Selected Change Committed Event" then i should get the record in the Output right but unfortunatly i am not getting the Record. The Record Count in DebugPrint showing 0.
[Code]...
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Jan 16, 2011
Considering that Grade.firstExam, Grade.secondExam, and Grade.finalExam are all TEXT and not numbers, i can't get the exact solution to convert null values into Zeros. I already tried to use NZ() but it returns an error message (Undefined Function 'NZ' in expression)im using VB.net with MS Access as my database. i also imported System.Data.OleDb Namespace.
[code]...
How can i convert empty string or null that exist in the field?
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Jun 9, 2012
I doing a project for my office. In that I am showing the values and strings from a particular table based on the date range and vendor selection. It is working fine with the date range. Except within the date range if the particular reader has no data it throws an error message like dbnull string.
[Code]...
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Nov 4, 2009
This should be simple but apparently it's not. I have a text file, 694 bytes. At byte 500 there's a null in the file. I've tried reading it as text and binary and I end up with a string, 694 bytes long. But anyting I do with this string fails because it appears to stop at character 500. I can do a ? asc(mystring.substring(549,1)) and I get 9 (tab). Print character 550 and I get 0. Print character 551 and I get 32 (space). How do I get rid of this null?
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Jun 24, 2011
The user will select an entry in a gridview, which then redirects them to a form that is populated with the data from the selected row (thus making the gridview editable in a more user friendly way). Null values are accepted by the DB and I would like to show null date values as blank (or " ") in the corresponding text boxes. Instead I get the error:
Conversion from type 'DBNull' to type 'Date' is not valid.
Here is my code:
'preceded by connection code
Dim sqlcmd As String = "SELECT * from Master WHERE RecNum = @recnum"
'Dim sqlCmd As New OleDb.OleDbCommand("SELECT * from Master WHERE RecNum = @recnum", connection)
Dim FileCommand3 As New OleDb.OleDbCommand(sqlcmd, connection)
[code]....
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Jul 4, 2010
How can I assign a variable which may contain a null value to a variable which is declared as Dim var1 as String and then use that variable to insert into access database table?
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Feb 1, 2010
Is there any way to convert null terminated string to normal string.I mean I can easily make a program to find the location of vbnull but there has to be a built in function for that.
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Feb 23, 2011
I get the following exception for the code shown below. The error occurs when i request access token.I downloaded the latest dll(2.3.1) from the twitterizer website.
{"Value cannot be null. Parameter name: String"}
Dim OAuthTokens As New OAuthTokens
Dim accessToken As New Twitterizer.OAuthTokenResponse
accessToken = OAuthUtility.GetAccessToken(ConsumerKey, ConsumerSecretkey, "oauth_token", "oauth_verifier")
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Sep 10, 2009
I have the following code below which has an error. When the checkbox is set to true and for example change the "role", and click save the following error is given;
"Index was outside the bonds of the array".
I know the reason of the error but don't know the solution..
The TxtPayCont is a concatenation of title, fname, and lname in an array. Therefore, if all the fields have values, then it works fine. So if it is Mr Jones Tim, this works, but, if it is Mr Jones it does not. It has to have 2 spaces to work. Is there anyway round this...
(see code below)..
Code:
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Oct 31, 2011
If I send a String set to Nothing as an input parameter to a SQL stored procedure, and in the sproc it's like this @MyString Char(9) = NULL, what does it turn NULL into? Because I'm firing the sproc and it's not firing the statement that says IF @MyString = NULL... So I don't know what it is... Or how can I pass the string as a NULL if nothing is passed as a parameter to my calling function?
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Jul 20, 2009
In my project i need to sign every end of a string with Binary NULL, how do I write Binary NULL?
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Jun 7, 2009
I'd like to convert a string which contains a decimal number into string that contains the binary value, the octal and the hexadecimal value of that decimal number.Afterwards I also like to convert a string containing a binary, octal and hexd. number into a decimal string.Basically I'm looking for the functions:
dec2bin
dec2oct
dec2hex
bin2dec
oct2dec
hex2dec
I'd not prefer to rewrite a function, I'm sure the framework must have these functions already.
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Jul 12, 2010
Currently, whenever I pass a string to the db, if that string is empty, then i set that object to NULL by doing the following:
IIf(DescriptionTxt.Text.length > 0, DescriptionTxt.Text, DBNull.Value)
I was thinking about writing a function to reduce the length of this code, and make it more consistent.However, I was wondering, is there already a way of doing this in .NET 3.5?
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Mar 26, 2010
I am using a com object to maniplate data inside an external program using VB.NET. One of the methods this com object provides requires 1 string parameter.The external program, however, requires a sting of a specified length, regardless of the number of characters used. The string to be passed to the function (length 36) is a combination of the below key fields.[code]I have tried the VB6 compatability's VBFixedString type but the com object's method throws an exception due to a type mismatch.If I convert the VBFixedString back to a .NET string before passing it to the method, the first null character is again interpreted as a string terminator and the rest of my string is chopped.
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Jun 29, 2011
I'm converting a system of numerous programs from foxpro/foxweb/javascript to asp.net/vb/sql server.
I'm coding for a dropdownlist which is currently controlled via js.
I don't like using the control this particular way, but I want to maintain look and feel for the customer.
The control is initialized with some values via Page_Load() in behind code.[code]...
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Jun 11, 2011
[Code]...
By my logic, this should only assign .length to index IF the length of strItem is longer than 0. This check is there in case the listbox is empty, or the user has not selected an item. However, everytime I go through this code without an item selected I get:
[Code]...
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Apr 15, 2009
Whats the best way to convert a list(of string) to a string with the values seperated by ,
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Dec 24, 2011
I need to convert a string array into a very long string with following requirement:
can not using any character escaping can not using XML can not using single character as separator (e.g. comma or space as separator)
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Sep 1, 2010
how can i convert these datatypes: date to string and integer to string.Because it must be in a string datatype when I display it in a datetimepicker and textbox.
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Mar 9, 2010
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.
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Jul 28, 2009
I'm using FileHelper to generate object's property. Here is an example of one property:
<FieldOptional(), _
FieldTrim(TrimMode.Both)> _
<FieldNullValue(GetType(String), " ")> _
Public StoreNo As String
As you can see the StoreNo will either have a value or " ", one of the business policy is to check if the StoreNo is empty or nothing if the object's StoreNo is empty or null then the record will not create.
I though about creating an HasValue Function in the class to check the StoreNo and other properties in the object but I feel like it is a hack.
Public Function HasValue() As Boolean
Dim _HasValue As Boolean = True
If StringHelper.IsNullOrBlank(Me.StoreNo) Then
[Code]....
I don't think this approach is an ideal solution. what if the StoreNo is remove or change to something else. What's the best approach to check object's property?
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Jan 4, 2012
I have a couple of textfields in a Windows form. One of these textfields is allowed to be NULL. When I enter a value for every field, it is all inserted, no problem. When I leave the field (txtGewicht) blank, I can't seem to be able to insert NULL in Access Database.
If Double.TryParse(txtGewicht.Text, 0) Then
klant.Gewicht = Double.Parse(txtGewicht.Text)
Else
[Code]....
This is what I get:
"Cannot set column 'Gewicht' to NULL, please use DBNull instead"
So I changed 'Nothing' to DBNull.value, but it then tells me that System.DBNull cannot be converted to type Double.
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Sep 21, 2011
I've moved my Database connection string into my app.config - however its causing a null exception error when i use it
App.Config
vb
<connectionStrings>
[Code].....
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Jun 17, 2010
I'm receiving a byte array from a network device by using the TcpClient class and as I have no idea how much data will be being sent I have to just declare a buffer that is X number of bytes long and keep reading into that until I've got all of the data. I then convert this byte array to a string using Text.Encoding.ASCII.GetString but the problem is that this gets any null bytes that were at the end of the buffer after the string and it includes them in the string. This then means when I do String.EndsWith it doesnt work as I would expect it to because there are just loads of 0 bytes at the end of the string.
Once I had realised that was what was happening (which took a long time as these null bytes are completely invisible when you are looking at the data in String form) I thought fine I'll just use Trim on the string but I've found that this doesnt make any difference at all. I thought Trim was supposed to remove any blank space from the start/end of a string, which I assumed would include empty bytes as well.
So is there any alternative I can use that will trim the empty bytes off the end or do I have to do it the 'manual' way and loop through my byte array before converting it to string and remove any null bytes? One thing that has just popped into my head as I'm typing this is to try using the Chr method and pass it 0 and combine that with Trim like so:
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Jun 28, 2010
This must've have been asked before but I couldn't locate it. In a mixed code project (VB and C#) we were debugging some old Visual Basic code where a statement as follows could be found:
If Request.Params("xxx") <> "" Then
'do something
I considered this a bug as Request.Params could be null, in which case the statement would've become false which wasn't the idea. So I thought. I just found out, -- probably for the tenth time and I will keep forgetting -- that the following two statements are not equal, while Nothing in VB should be equal to null in C# (thought I):
if(String.Empty == null) // always false
If String.Empty = Nothing Then ' always true
Should I dismiss this as a typical Microsoft backward compatibility effort, or should I consider this a huge error in the VB.NET compiler? Does anybody know the Microsoftean opinion on this oddity?
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Nov 9, 2009
how I can convert an RTF String to a regulat text string. The rtf string has tons of formatting info, but all I need is the text in the string.
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Aug 3, 2011
Currently, I'm using the following code to pull info from the management class.
[code]...
I'm also pulling info from the bios, disk drives, video, etc. What I've noticed, is although it runs fine on my pc, it may error out on some pcs since it is hardware dependent.I'm having trouble implementing a check to find if it exists before I convert to a string and add it to my overall string.
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