I have the following POCO:
Public Class T1
<Required()>
<MaxLength(128)>
<Key(), Column(Order:=0)>
Property K1 As String
[Code]...
I would expect C2 to be created as Nullable, but both C1 and C2 are Not Null. Adding
<Required(AllowEmptyStrings:=True)>
Does not make a difference, as it seems the decoration is aimed at data validation, not DB creation.
So how do i get a nullable column with Code First?
I'm trying to do something similar to what's described here, but with nullable types.
[URL]
int availableUnits = unitsInStock ?? 0;
In VB, it would be this:
Dim availableUnits As Int32 = If(unitsInStock, 0)
However I'm working with db columns, which could be DbNull, and nullable types, which can be Nothing (which is different to DbNull). If a column is DbNull, I want to return Nothing, otherwise return the value. For eg:
Dim availableUnits As Int32? = If(myDataReader("UnitsInStock").Value, Nothing)
The error I'm getting is "Specified cast is not valid" but I'm not sure why. I've tried this as well:
Dim availableUnits As Int32? = If(isDbNull(myDataReader("UnitsInStock").Value), myDataReader("UnitsInStock").Value, Nothing)
Which is messy and just results in the same error. The only thing that works is this:
Dim availableUnits As Int32?
If isDbNull(myDataReader("UnitsInStock").Value) Then
availableUnits = myDataReader("UnitsInStock").Value
Else
availableUnits = Nothing
End If
Which is just silly. Is there a better way of getting nullable db values into nullable variables that I'm not aware of?
I'm working against a SQL Server database that regularly has DateTime columns that can be null. I'm using LINQ to SQL to connect my WinForms (VB.NET) program to the data. I've extended some of the LINQ objects and added a couple of Nullable(Of DateTime) properties. Basically, I'm calculating whether a particular value exists. The value is a DateTime. If it doesn't exist, I want to create a Nullable(Of DateTime) object (structure, whatever) with the HasValue property set to False.
[Code]....
[Code] Now the problem is that after i put this user-control in a form, I have to set a value for the Handled file. Otherwise it gives me a value cannot be null exception. Is there a way that i can set code that would execute in the case of the value being null? [Code]
View 14 RepliesSo I'm building an application that is going to do a ton of code generation with both C# and VB output (depending on project settings). I've got a CodeTemplateEngine, with two derived classes VBTemplateEngine and CSharpTemplateEngine. This question regards creating the property signatures based on columns in a database table. Using the IDataReader's GetSchemaTable method I gather the CLR type of the column, such as "System.Int32", and whether it IsNullable. However, I'd like to keep the code simple, and instead of having a property that looks like:
[Code]...
How can I create a nullable numeric optional parameter in VB.NET?
View 3 RepliesVB GridView control will not allow code in the vb code file to access a data column that has its visible property set to false. When it is set to true, the data column can be accessed with no problem. Any suggestions as to how to correct this? I have looked through the documentation, text books, and I have not found anything that gave me any clue as to what the problem could be. I thought that the property was just applied to the column, not that it would remove the column from being accessible.
[Code]...
I accidently wrote some code today that was like this[code]...
I immediately noticed the issue, but I had already hit the run button. It compiled successfully, I ran it through to the section and it threw an exception.
You can't do this in C#, it gives a compile error "cannot convert from 'int?' to 'int'".
Is there an 'Option Explicit' type switch that I can turn on to ensure that this sort of error does not occur again?
I have created reports that print on my printer via Visual Studio 2008/VB 2008 Basic code. I want to be able to send these reports to other people via emai. I don't care how its done, but it seems that if I could get the report into Word 2007 the problem would be solved. What are your suggestions to accomplish my objective.Terry 01
View 1 RepliesI am using the following to strip out unwanted string in a string and i want to fill newly created column with split value. I dont know how to get the "Cityrev" into a column value[code]....
View 4 Repliesi want to create column headers now in my first array have this [URL]
array
CSC238,8.00-9.50
MAT183,1.00-2.00
ECO120,2.10-4.00
[code].....
My below code pulls in 100 items into the checkboxlist all into one column. How can I modify the code so it will appear as two columns?
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
Dim di As New IO.DirectoryInfo(ImagePath)
Dim imageArray As IO.FileInfo() = di.GetFiles()
Dim image As IO.FileInfo
'list the names of all images in the specified directory
For Each image In imageArray.OrderBy(Function(i) i.Name)
CheckBoxList1.Items.Add(image.Name)
Next
End If
End Sub
obcon.cmd.CommandText = " select f_name + ' ' + m_name + ' ' + l_name from contact where type='" & ledcmbsrctype.Text & "'"
obcon.con.Open()
Dim dr As SqlDataReader
[code]....
'name is added to combo box and i want to get id for selected name.
is there a date datatype in visual studio 2008? cause i want to create a column name with date as its datatype.. but the one that comes out is datetime..
View 4 RepliesI need to create and populate a ListView with 3 strings that come from another function. I also want to be able to select multiple pieces of the data to change their values during runtime (is that possible with ListView?).
I've looked all over online for info on this, but I can't seem to find any.
I've seen somethings on GridView as well. Would that be better for this application?
Can someone tell me please if it is possible to create a datacolumn(LowestPrice), and using something like MIN expression, have this column (LowestPrice) populated with the lowest amount from 3 columns on the same row.[code]If possible could someone please provide the syntax or code for this to work
View 7 RepliesHow to create 2 column in combobox1?
View 1 RepliesI am trying to figure out how to write code for a for/next loop that will retrieve a particular column, or field to add the grand total of the objects located therein. This is what I have:
Private
Sub subCalculate()
'this sub is used to figure and list the total price of the selected category
Dim drArray() As DataRow
Dim pintCount As Integer
Dim pdecTotal As Decimal
[code]...
Using MS Access 2003 I am trying to build a command button in a form which clears the contents of a table column (which are tick boxes) - the idea behind it is this - the database is a contacts database for a club. Every year there is a subscription to be paid, so I want a column to annotate those who have paid (using a tick box). At the end of the year this will be reset - hence the reason for trying to produce a command button that clears out the ticks. What I using is this ....Private Sub Command11_Click()Dim strSQL As StringstrSQL = "UPDATE TBL-Master SET TBL-Master.campaign = '';"DoCmd.RunSQL strSQLEnd Sub(TBL-Master is the table name, campaign is the column name)What I am getting is a runtime error - 3144 -
View 3 RepliesIs there a way to set the size of each column's width in code?
*i have used this code to view my databse into my datagrid [code]...
I have a range in excel and I want to be able to sort it by one column programmatically.
There is range.sort, but it has a ridiculous about of parameters and I cannot get it to work.
Surely there must be something to be able say I want this data to be sorted by this column?
how to write a code in vb2005 to create an sql database
View 2 RepliesI'm using vb.net, and I can't figure out how to code a picturebox that I create in the code.
View 2 RepliesI am writing a macro using excel 2003 to read rows of a excel sheet & perform some task,now before execution I want the user to select for which rows the operation is to be performedo do so I added a form in MACRO & placed a flexgrid on the form which will display the content of the excel sheet. But, I am not able to change a column type to a checkbox where the user can check it to indicate if the operation is to be performed on that row or not.
View 2 RepliesI'm trying to create a multi column combo box in VB.net.[url]...
It just does not like the class="MSONormal" statement at the beginning.
create form with 5 column system of textboxes?
View 1 RepliesFor my database I need to create unique numbers and insert them in the column "ID". Can I add them via a SQL query? The numbers would simply be 0001 to whatever.I'm using the "Show Table Data" gui.
View 7 RepliesI am trying to create a datagrid with combobox column and here is what I have so far.
Imports System.Data.SqlClient
Public Class frmSectioningByLevel
Private cnn As New SqlConnection(My.Settings.ConnectionString)
[code]....
1. how do I just display the concatenated student name in my datagridview?
2. how do I add combobox column in my datagrid? The combobox values will be coming from tblSection's SectionName field.
3. After I will assign section name to each students, I will be updating my table with a click of a button. How do I tell VB to update tblenrol with the assigned section for every students?
I have a table in database which I need to add a new column to. Normally I would load the access database and create the column but in this instance I have to many databases to amend. Is there a way in code to first detect if the column exists and if it doesn't create it in code?
View 1 RepliesI want to create column headers. Now in my first array have this
array
CSC238,8.00-9.50
MAT183,1.00-2.00
ECO120,2.10-4.00
BEL311,4.10-6.00
MAT183,8.00,9.50
Then second array, I want to do like this
array
8.00-8.50
9.00-9.50
10.00-10.50
11.00-11.50
12.00-12.50
1.00-2.00
2.10-3.00
3.10-4.00
4.10-5.00
5.10-6.00
6.00-7.00
7.00-8.00
8.00-8.50
9.00-9.50