When using the If operator [URL] to assign a value to a System.Nullable object, if the result is Nothing (null), then 0 is assigned to the object. Example: 'Expected value is null (Nothing). Actual value assigned is 0. Dim x As System.Nullable(Of Integer) = If(1 = 0, 1, Nothing) If x is a nullable type, why is it being assigned the default integer type of 0. Shouldn't it receive a value of null?
View 2 Replies
I have a structure that contains another structure. The inner structure is nullable. Now wht I do is something like the following. I create a new instance of the inner structure, set the member variables and assign the whole structure to the inner structure of the parent. But it is giving an error. The assignment is not successful. If I try to peek into the structure in the watch window, it says "property evaluation failed" for the HasValue and Value properties.
Dim testData As List(Of TestData) = Nothing
Dim testData_List1 As New TestData
With testData_List1.commonTestParam
[Code].....
Why does this give variable A the value of zero (instead of setting it to nothing)?Dim A as double? A=If(2<3, Nothing, 6)
View 11 RepliesI have a Job Register Table and that table doesn't have any records.
This is my LINQ code:
Dim QRecordCount = (From LC In CntxtJobDetails.JobRegistrations _
Where LC.JobCode <> 0 _
[code].....
When i execute this linq to sql command its given an error "The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type." 0 Records in my Commotidy Table
I want generate manual number and get the last CommodityCode.My Code as follow,
Dim QRecordCount = From RC In cntxtCommodity.CommodityMasters _
Where RC.CommodityCode <> 0 _
Select RC.CommodityCode[code].....
I am trying to concate string and system.type using operator & in VB and i am getting error :
[Code]...
I'm having problems with a Nullable DateTime in VB.NET (VS 2010).
Method 1
If String.IsNullOrEmpty(LastCalibrationDateTextBox.Text) Then
gauge.LastCalibrationDate = Nothing
[code].....
dim val1 As Integer? = If(5 > 2, Nothing, 43)' val1 = 0 dim val1 As Integer? = If(5 > 2, Nothing, Nothing)' val1 = Nothing What gives? Is this a bug, or am I overlooking something?
View 1 RepliesThe following compiles in VB.NET (with Option Strict On) and outputs False:[code]Why does that work?The documentation clearly states that the three-argument version of If requires a Boolean as the first parameter:[code]So, why does this work? Is it a bug (or "hidden feature") in the compiler or is it a bug in the documentation and Boolean? is actually a valid type for the first argument of If(a, b, c)?In C#, b ? x : y does not compile if b is of type bool?.I've reported this issue to Microsoft Connect. Someone from MS has replied and confirmed that the documentation will be updated to include the Boolean? case.
View 4 RepliesIf you assign a value to a nullable integer via a ternary operator, it can't become null..While this question may seem like a duplicate of many, it is actually being asked for a specific reason.Take this code, for example: Dim n As Integer? = If(True, Nothing, 1) In that code, the ternary expression should be returning Nothing, but it's setting n to 0. If this were C#, I could say default(int?) and it would work perfectly. Now it looks like I am going to have to ditch the ternary and use a regular If block, but I really want to use the ternary. If Nothing were truly VB.NET's equivalent to C#'s default, how can you explain this behavior?
View 1 RepliesMy program has decided to assign pointers instead of make copies of an object, and I'm not sure why. I have something like this:
Public Class Foo
Private myFooData As New List(Of FooData)
Public Sub New(ByVal newFooData As List(Of FooData))
[Code]....
Very simplified, but basically what I'm doing. So for some reason today when I change item in newFoo.FooValues, originalFoo.FooValues also changes, and mainFoo does not. I've tried assigning the entire objects as well and I get the same results.
I would expect the following vb.net function to return a value of Nothing, but instead its returning a value of 0.
[Code]...
So I'm writing the equality operator overload (Operator =())for a custom object, and the resulting mess of If conditionals is just an eyesore. But so far, it seems like the only sane way to check the values to as to match the specific behavior of this object.
The rules are:Num1 is required, period, and both the left and right operands and must be equal for True. Else, False.Num2 is optional, but if specified, must be present for both the left and right operands, and must be equal for True. Else, False.Num3 is optional, but can only be specified if Num2 is also present. Else, False.Num3, if specified, must be present for both the left and right operands, and must be equal for True. Else, False.
[Code]..
I also know that I could cache elements of the checks into booleans and then use those to reduce the amount of text. But that seems like a waste of cycles just for code readability. So I wanted to know if the SO community had better thoughts on reorganizing it, just in case I'm being too verbose with my checks.
I have a generic Class I'm using to hold information loaded from a database.I have a method which takes a DataRow as an argument, uses the object's known column name and extracts the data from the DataRow, such that:Dim loadData As T = CType(myDataRow("myColumnName"), T))works as my default assignment in most cases.Unfortunately, due to some horrifying design constraints, some of my columns may be null, and may also be taken from enumerations.This means that when <T> is Nullable(Of SomeEnumeration) the above code does not work because I can't cast 0 directly to SomeEnumeration.Zero.Is there some way to check whether <T> is Nullable(Of [Enum])? Or some way to write a method which allows Integers to be cast to Nullable(Of [Enum])?I feel like I'm forgetting something that would allow me to write one of the other of these, but my weak google-fu is turning up nothing.
EDIT: Okay, thanks to dasblinkenlight's answer below, I can detect when this circumstance is occurring, but what I need to do now is to take a type <T> which I know is Nullable(Of SomeClass), get a type reference to SomeClass and then create a new object of type Nullable(Of SomeClass) and assign that to LoadData.My problem was that I had a lot of difficulty in finding any function which would accept baseType as an actual Type.Parse accepted baseType as a parameter, I knew baseType was an [Enum] type because of dasblinkenlight's code, so I was, in this instance, able to code a solution. It's a solution which is very specific to my problem (i.e., T is Nullable(of SomeEnumeration)), but it's a solution nonetheless.
I'm having trouble assigning values to an array and am getting the error, "Value of type MemberFocal.Member cannot be converted to System.Array" - MemberFocal.Member is part of a custom class and I am attempting to create an array of these objects. Here is the code:
[Code]....
Im working on my first n-tier application. I am trying to serialize a structure and Im getting an error"Soap Serializer does not support serializing Generic Types : System.Nullable`1[System.DateTime]."Here is the structure that is being serialized
Namespace Structures
<Serializable()> _
Public Structure structAllergy
Public AllergyID As String
Public ProfileID As String
[code]....
The bold line is the line that is throwing the error.
I am tightening up my coding with the Option Strict set to ON. It has now produced alot of errors. An example of this is:
If AllocatedDGV.Rows(i).Cells("RoomNumber").Value = RoomsAvailableDGV.Rows(j).Cells("RoomName").Value Then
It gives me the following error: Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity.
I need to write an interface to get data to/from our data files.
We have a low level class that holds field values for each record read from the files.
This just holds two values, the value read from the file (DBValue) and the updated value that may need to be written back to the file (CurrentValue).
These values may be any of the standard value types (integer, date etc) or a string.
Either value (DBValue or CurrentValue) may be null if not defined.
I have written the class to manage this data which works fine while option strict is NOT on.
But we have an office policy of having option strict on all the time.
When I put option strict on, my object value comparisons fail with the error: "Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity."
Question, how should I change the following code to handle option strict on ...
This is all running on Visual Studio 2010
[Code]...
VB 2008, DataGridView,DataGridView1_CellLeave(sender, New System.EventArgs)
"Unable to cast object of type 'System.EventArgs' to type 'System.Windows.Forms.DataGridViewCellEventArgs'."
What is the Correct String for "New System.EventsArgs"
Anybody there is to help me out.
This is my
[Code]...
This is my error: Operator '=' is not defined for type 'FileInfo' and type 'Boolean'.
Public Pixels(0 To 95, 0 To 127) As Variant Red = Pixels(X, Y) And &HFF i get this code from VB6, and when i transfer to VB05 i got problem said " Operator 'And' is not defined for type 'Color' and type 'Integer'. " i sent to VS2005
Public Pixels(0 To 95, 0 To 127) As Object
Dim red As Object
Red = Pixels(X, Y) And &HFF
In my application when i click the button i'm getting this" Operator '=' is not defined for type 'Char' and type 'Boolean'." But when i test it locally there is no problem at all!
View 2 RepliesI'm getting an error after sending a list to a web service.This is the code that is calling the web service:
Dim sProgramInterest As New List(Of Integer)
crmService.InsertProspectGetId(sProgramInterest.ToList)
But I'm getting this error.
[code].....
My project worked a first and now its giving me a problem.The error
Quote:
Unable to cast object of type 'System.Windows.Forms.MouseEventArgs' to type 'System.ComponentModel.RunWorkerCompletedEventArgs'.
[URL]The issue is as soon as I change the value of the text boxes it gives me an error and forces me to close the project.
The error is:Unable to cast object of type 'System.EventArgs' to type 'System.Windows.Forms.KeyPressEventArgs'.
However I'm supposed to clear the number of gallons used and the total charged when a change is made to the contents of the 2 text boxes on the form.
I have an InvalidCastException Error in my program. The program is that i try to insert an employee record into a database table after getting the details from a form. I've used Money data type is SQL Server for salary and SqlTypes.SqlDecimal data type in employee template class. i've used a stored procedure to pass the values and i add the basic value by passing a parameter by the method
Dim prm8 As SqlParameter = com.Parameters.Add("@basic", SqlDbType.Money)
prm8.Direction = ParameterDirection.Input
prm8.Value = emp.Bsc
I've used the money datatype itself even in the stored procedure variable.I get the following error.
failed to convert parameter value from sql decimal to decimal
Even if i use
prm8.Value = Convert.ToDecimal(emp.Bsc)
I get an error Unable to cast object of type 'System.Data.SqlTypes.SqlDecimal' to type 'System.IConvertible'.
Now I want to display picture in picturebox1.To do this I use this codes, but it does not display picture
on this line: Dim arrPicture() As Byte = CType(dt2.Rows(0)("img_path"), Byte())
it shows this message,
Unable to cast object of type 'System.DBNull' to type 'System.Byte[]'.[code]......
I am getting this error when I am tring to load string type to data table)
Using connection As New SqlConnection("connectionstring;")
connection.Open()
Using Command As New SqlCommand("SELECT ClientId,forename,surname from t_clientdetails
[code].....
I get the below error Unable to cast object of type 'System.String' to type 'System.Data.DataTable'.This is the code I'm using
Dim str As String = String.Empty
If (Session("Brief") IsNot Nothing) Then
Dim dt As DataTable = Session("Brief")
If (dt.Rows.Count > 0) Then
[code]....
Unable to cast object of type 'System.String' to type 'System.Windows.Forms.TextBox'.
View 12 Replies
