VB .net program to accept Null Values

[Bigga Lexx]

I am new to the VB .NET programming language. Actually I want to ask that is there any way to write a program that can accept the null values. Even if possible tell me how to do in SQL also. I am having the following value :
CheckString(RemoveCarriageReturns(dreader.GetString(2)))
And I want to insert this value into a table. Also I want that this value should accept the Null Values. Can someone help me in solving my query.?? Please help me soon.
Extremely Thanks in Advance.

[Zecho]

When the application expects a data value and gets nothing or unexpected values then the Null or nonexistent data gets complicated. So you will have to perform coding that properly handles these situations to avoid application failure. The default value of reference-type variables is null. A null value is a value that doesn't refer to any object. That's why this requires a close examination of the data wherever and whenever it's needed. There's no VB.NET equivalent of the null keyword like in another programming language like C#. VB.NET uses the Nothing keyword. The following code is an example of the Null value :

Dim sTest As String
If (sTest Is Nothing) Then
Console.WriteLine("sTest is Null")
End If

Also the VB.NET doesn't treat null and Nothing as equals. So the programmer that is writing a code in VB .NET will have to check the possibility for both the values.

[Katty]

As you said that you want the code that your value can accept the Null Value. And CheckString(RemoveCarriageReturns(dreader.GetStrin g(2))) was your value. So the code in VB .NET will be :

dbconnection2.Open()
dbcommand2.CommandText = "select orderitemid,qty,description,despatched from tblorderitem where orderid = " & gloOrderID
dreader = dbcommand2.ExecuteReader
While dreader.Read
dbconnection.Open()
dbcommand.CommandText = "insert into " & tmptable & " (orderitemid,qty,description,despatched,outstanding,thisdelivery) values(" & dreader.GetInt32(0) & "," & dreader.GetInt32(1) & ",'" & CheckString(RemoveCarriageReturns(dreader.GetString(2))) & "'," & dreader.GetInt32(3) & "," & dreader.GetInt32(1) - dreader.GetInt32(3) & ",0)"
dbcommand.ExecuteNonQuery()
dbconnection.Close()
End While

[kelfro]

If you want to work with null values, then the Microsoft provides a uniform method for working with null values: The base System.Convert namespace includes the DBNull object. The absence of a known value is indicated by the use of the DBNull class. This class differentiates between a null value (a null object) and an uninitialised value (the DBNull.Value instance). A null object is a valid value for a field in database applications. A table can have records with uninitialised fields. These uninitialised fields have the DBNull value. The VB.NET sample for the DBNull value will be like this :

If (sTest.Equals(System.DBNull.Value) Then
Console.WriteLine("sTest is Null")
End If

[Praetor]

You do system.dbnull, if the SQL data type is NOT a string type or numeric type. If it is numeric then 0 and if it's a string type (char, text, formatted text,) you do "". The null value applies to a very restricted group. Also before passing the value to SqlDataReader, check whether the value is "" . If it is, pass System.DBNull.Value and check. NULL values require special handling in SQL queries. NULL represents an unknown value, and strictly speaking NULL is never equal to NULL. In SQL, the Null values should be treated cautiously, particularly in ALL, ANY, IN and EXISTS queries.

[opaper]

The following code can be used to check the Null values in VB .NET :

Public Function CheckDBNull(ByVal obj As Object, _
Optional ByVal ObjectType As enumObjectType = enumObjectType.StrType) As Object
Dim objReturn As Object
objReturn = obj
If ObjectType = enumObjectType.StrType And IsDBNull(obj) Then
objReturn = ""
ElseIf ObjectType = enumObjectType.IntType And IsDBNull(obj) Then
objReturn = 0
ElseIf ObjectType = enumObjectType.DblType And IsDBNull(obj) Then
objReturn = 0.0
End If
Return objReturn
End Function

Before doing this main program you will have to declare the following values :

Enum enumObjectType
StrType = 0
IntType = 1
DblType = 2
End Enum