I'am new in LINQ.
I am trying insert one row into SQL table via LINQ, but with error: Value of Type 'sendStatus.OnePerson' cannot be converted to 'iloTest'
I tried SELECT as well, and its working => connection to db is OK
This is my code:
Protected Structure OnePerson
Property name As String
Property password As String
End Structure
Protected Sub btnInsert_Click(sender As Object, e As System.EventArgs) Handles btnInsert.Click
Using dbContext = New sampleDataContext
Dim newPerson = New OnePerson
newPerson.name = "myName"
newPerson.password = "myPass"
dbContext.iloTests.InsertOnSubmit(newPerson)
dbContext.SubmitChanges()
getData()
End Using
End Sub
I'm using the RegisterProperty from CSLA. I also have DisplayAttribute and DisplayNameAttribute on my properties attached to a resource. I notice that the .Name property of each of my RegisterProperty are cached. If I switch language, the .Name is not refreshed. This causes trouble since I'm using StringLengthAttribute and others to handle some business rules.
Is there a way to refresh the .Name or make sure the value isn't cached?
For now I decided to create my own attribute that takes the display name as parameter. I which there was a way to disable caching.
Public Class StringLengthExAttribute
Inherits StringLengthAttribute
Private _displayResourceName As String = ""
Public Sub New(ByVal maximumLength As Integer)
MyBase.New(maximumLength)
Me.ErrorMessageResourceName = "ruleExceedMaxCharacter"
Me.ErrorMessageResourceType = GetType(My.Resources)
End Sub
Public Sub New(ByVal displayResourceName As String, ByVal maximumLength As Integer)
MyBase.New(maximumLength)
_displayResourceName = displayResourceName
Me.ErrorMessageResourceName = "ruleExceedMaxCharacter"
Me.ErrorMessageResourceType = GetType(My.Resources)
End Sub
Public Overrides Function FormatErrorMessage(name As String) As String
If _displayResourceName <> "" Then
name = My.Resources.ResourceManager.GetString(_displayResourceName)
End If
Return MyBase.FormatErrorMessage(name)
End Function
End Class
i have ASP.NET page, its code-behind, and a Class file:
Folder1/page.aspx (asp.net page), it contains a label:
<asp:Label runat="server" ID="Label1" Visible="false"></asp:Label>
Folder1/page.aspx.vb (code-behind), it calls connection.vb like this:
Dim x As New Connection
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
x.checkusernameExists(TextBoxUsername.Text)
' I try to access `Boolean variable` Flag from Class file but I can't.
End Sub
App_Code/connection.vb (a class file that i created):
Public Class Connection
Public Sub checkusernameExists(ByVal username1 As String)
Dim flag as Boolean
' I try to access here `Label1.text` & `Label1.visible` to work on it but I can't.
End Sub
End Class
My Questions
1 - How can I access the Label1 from the ASP.NET page in Connection.vb?
2 - How can I access the Boolean variable from Connection.vb in page.aspx.vb (code behind)?
I am really stuck in this.
Thank you.
Use (public) properties or method parameters.
You have to ask yourself following: why should a class that is responsible for a connection(i assume to database) have access to your GUI at all? Don't hardlink different layers with each other, otherwise you won't be able to use them alone.
I would suggest to let the connection class do it's work and that is not to modify your frontend. Instead the controller (the aspx page) should manage it's GUI and call the connection class, using the return value to determine what to do next with the Label.
So return a Boolean to indicate if the user is valid:
Public Class Connection
Public Shared Function checkusernameExists(ByVal username1 As String)As Boolean
Dim userExists As Boolean
' acces db to check if the username exists '
Return userExists
End Sub
End Class
in your page:
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
Dim userExists As Boolean = Connection.checkusernameExists(TextBoxUsername.Text)
Label1.Visible = userExists
If Label1.Visible Then Label1.Text = "Hello again " & TextBoxUsername.Text
End Sub
make flag as property and set this property in checkusernameExists function
Public Class Connection
Public Property Flag as Boolean
Public Sub checkusernameExists(ByVal username1 As String)
// set flag here
Flag = True // or whateever value returned from the database
' I try to access here `Label1.text` & `Label1.visible` to work on it but I can't.
End Sub
End Class
and access this instance level property in page.aspx.vb file
Dim x As New Connection
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
x.checkusernameExists(TextBoxUsername.Text)
Label1.Visible= x.Flag;
' I try to access `Boolean variable` Flag from Class file but I can't.
End Sub
You can use Function to return value and pass label as parameter.
Public Function SaveChanges(ByRef Label1 As Label, ByVal username1 As String) As Boolean
{
Return True
}
It would be better if you pass the label properties to function instead of passing the object of label as it couple up two classes.
I tried to make some experiment today. I have an application that uses untyped datatables as the model entities.
They are all made like:
Imports System.Data
Imports System.Runtime.Serialization
Imports System.ComponentModel
<DesignerCategory("Code"), system.Serializable()>
Partial Public Class SomeTable1
Inherits DataTable
#Region
Public Const TABLE_NAME As String = "SomeTable1"
Public Const FIELD_SomeField1 As String = "SomeField1"
Public Const FIELD_SomeField2 As String = "SomeField2"
#End Region
Protected Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext)
MyBase.New(info, context)
End Sub
Public Sub New()
MyBase.New()
With Columns
.Add(FIELD_SomeField1, GetType(System.String)).DefaultValue = String.Empty
.Add(FIELD_SomeField2, GetType(System.Double)).DefaultValue = 0
End With
Dim keys(1) As DataColumn
keys(0) = Columns(FIELD_SomeField1)
TableName = TABLE_NAME
PrimaryKey = keys
End Sub
End Class
I'm currently working with EF, so in my razzle, I wrote something like this (yeah, it's vb):
Partial Public Class SomeTable1
Inherits DataTable
<Key()>
Friend Property SomePK1 As DataColumn
<Required(ErrorMessage:="SomeField1 is required.")>
<DataType(DataType.Text)>
Friend Property SomeField1 As DataColumn
<Required()>
<DataType(DataType.DateTime)>
Friend Property SomeField2 As DataColumn
...
Protected Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext)
MyBase.New(info, context)
End Sub
Public Sub New()
MyBase.New()
SomeField2 = Date.Now
End Sub
End Class
I was dreaming on making something equivalent to the former dt and being completely compatible with the current data engine.
And then the type conversion error (system date to datacolumn) broke my hopes. I must admit that has been a hard weekend :)
So before I completely discard the change, Is there any way of writing a Typed datatable so it's equivalent to the code above but with some new goodies?
That's so ancient way of programming I can't find anything on the net.
Thanks in advance.
Not sure I'm following completely but it looks like you're defining FIELD_SomeField2 as a double
(This Line in first snippet)
.Add(FIELD_SomeField2, GetType(System.Double)).DefaultValue = 0
But then I see you're defining SomeField2 as a DateTime in your second snippet.
<Required()>
<DataType(DataType.DateTime)>
Friend Property SomeField2 As DataColumn
So maybe just a type mismatch...
I found how to do what I wanted. Perhaps involves some work, but it works.
Knowing that this is such an obsolete way of doing things, I'm posting there so others like me that are forced to maintain old programs can benefit.
The template for doing a typed datatable is the following:
Imports System.Data
Imports System.ComponentModel
Imports System.Runtime.Serialization
Imports System.Diagnostics
'''<summary>
'''Represents the strongly named DataTable class.
'''</summary>
<Global.System.Serializable(), _
Global.System.Xml.Serialization.XmlSchemaProviderAttribute("GetTypedTableSchema")> _
Partial Public Class tblMyTable
Inherits TypedTableBase(Of tblMyTableRow)
'Those are the StoredProcs names for (MANUAL) CRUD operations that the DBContext wrapper uses. (yuck! I hate thousands of them)
'Public Const COMMAND_SAVE As String = "sp_MyTable_Save"
'Public Const COMMAND_DELETE As String = "sp_MyTable_Delete"
'Public Const COMMAND_LOADBY_ID As String = "sp_MyTable_LoadBy_Id"
'Those are constants I maintain for untyped (but somewhat strong) compatibility
Public Const FIELD_pID As String = "pID"
Public Const FIELD_SomeOther As String = "SomeOtherField"
'Basic CRUD, uses company data as the app hot swapps DBs (one for company)
'Public Function Save(ByVal company As DataRow) As Short
' Return New Base(company).Update(Me, COMMAND_SAVE, COMMAND_DELETE)
'End Function
'Public Sub LoadByID(ByVal company As DataRow, Id As Integer)
' Me.Rows.Clear()
' Me.Merge(New Base(company).FillDataTable(Of tblMyTable)(COMMAND_LOADBY_ID, Id))
'End Sub
<DebuggerNonUserCodeAttribute()>
Private Sub InitClass()
Me.columnpID = New DataColumn(FIELD_pID, GetType(Integer), Nothing, MappingType.Element) With
{.AllowDBNull = False, .ReadOnly = True, .Unique = True,
.AutoIncrement = True, .AutoIncrementSeed = -1, .AutoIncrementStep = -1}
MyBase.Columns.Add(Me.columnpID)
Me.columnSomeOtherField = New DataColumn(FIELD_SomeOther, GetType(String), Nothing, MappingType.Element) With
{.MaxLength = 5, .AllowDBNull = False, .DefaultValue = String.Empty}
MyBase.Columns.Add(Me.columnSomeOtherField)
End Sub
Private columnpID As DataColumn
Private columnSomeOtherField As DataColumn
<DebuggerNonUserCodeAttribute()>
Public Sub New()
MyBase.New()
Me.TableName = "tblMyTable"
Me.BeginInit()
Me.InitClass()
Me.EndInit()
End Sub
<DebuggerNonUserCodeAttribute()>
Friend Sub New(ByVal table As DataTable)
MyBase.New()
Me.TableName = table.TableName
If (table.CaseSensitive <> table.DataSet.CaseSensitive) Then
Me.CaseSensitive = table.CaseSensitive
End If
If (table.Locale.ToString <> table.DataSet.Locale.ToString) Then
Me.Locale = table.Locale
End If
If (table.Namespace <> table.DataSet.Namespace) Then
Me.Namespace = table.Namespace
End If
Me.Prefix = table.Prefix
Me.MinimumCapacity = table.MinimumCapacity
End Sub
<DebuggerNonUserCodeAttribute()>
Protected Sub New(ByVal info As Global.System.Runtime.Serialization.SerializationInfo, ByVal context As Global.System.Runtime.Serialization.StreamingContext)
MyBase.New(info, context)
Me.InitVars()
End Sub
<DebuggerNonUserCodeAttribute()>
Public ReadOnly Property pIDColumn() As DataColumn
Get
Return Me.columnpID
End Get
End Property
<DebuggerNonUserCodeAttribute()>
Public ReadOnly Property SomeOtherFieldColumn() As DataColumn
Get
Return Me.columnSomeOtherField
End Get
End Property
<DebuggerNonUserCodeAttribute(), Browsable(False)>
Public ReadOnly Property Count() As Integer
Get
Return Me.Rows.Count
End Get
End Property
<DebuggerNonUserCodeAttribute()>
Default Public ReadOnly Property Item(ByVal index As Integer) As tblMyTableRow
Get
Return CType(Me.Rows(index), tblMyTableRow)
End Get
End Property
<DebuggerNonUserCodeAttribute()>
Public Overrides Function Clone() As DataTable
Dim cln As tblMyTable = CType(MyBase.Clone, tblMyTable)
cln.InitVars()
Return cln
End Function
<DebuggerNonUserCodeAttribute()>
Protected Overrides Function CreateInstance() As DataTable
Return New tblMyTable()
End Function
<DebuggerNonUserCodeAttribute()>
Friend Sub InitVars()
Me.columnpID = MyBase.Columns(FIELD_pID)
Me.columnSomeOtherField = MyBase.Columns(FIELD_SomeOther)
End Sub
<DebuggerNonUserCodeAttribute()>
Public Function NewtblMyTableRow() As tblMyTableRow
Return CType(Me.NewRow, tblMyTableRow)
End Function
<DebuggerNonUserCodeAttribute()>
Protected Overrides Function NewRowFromBuilder(ByVal builder As DataRowBuilder) As DataRow
Return New tblMyTableRow(builder)
End Function
<DebuggerNonUserCodeAttribute()>
Protected Overrides Function GetRowType() As Global.System.Type
Return GetType(tblMyTableRow)
End Function
<DebuggerNonUserCodeAttribute()>
Public Sub RemovetblMyTableRow(ByVal row As tblMyTableRow)
Me.Rows.Remove(row)
End Sub
End Class
'''<summary>
'''Represents strongly named DataRow class.
'''</summary>
Partial Public Class tblMyTableRow
Inherits DataRow
Private tabletblMyTable As tblMyTable
<DebuggerNonUserCodeAttribute()>
Friend Sub New(ByVal rb As DataRowBuilder)
MyBase.New(rb)
Me.tabletblMyTable = CType(Me.Table, tblMyTable)
End Sub
<DebuggerNonUserCodeAttribute()>
Public Property pID() As Integer
Get
Return CType(Me(Me.tabletblMyTable.pIDColumn), Integer)
End Get
Set(value As Integer)
Me(Me.tabletblMyTable.pIDColumn) = value
End Set
End Property
<DebuggerNonUserCodeAttribute()>
Public Property SomeOtherField() As String
Get
Return CType(Me(Me.tabletblMyTable.SomeOtherFieldColumn), String)
End Get
Set(value As String)
Me(Me.tabletblMyTable.SomeOtherFieldColumn) = value
End Set
End Property
End Class
That's all that you need. Perhaps It could be reduced, but then the dataset functions would not work as expected.
If you want that code, generated automagically for you by the ID (VS2010) you must follow those steps:
On server explorer, create the connection to your favorite DB
Right-click on top of your project and select adding a new element.
Just pick the dataset object template, the name is irrelevant. It will open in designer view.
Pick the table from the database and drag to the dataset designer.
Then... look at the class selector on top.
Unfold and locate [yourTableName]Datatable. Click on it.
It will jump to the said class in the DataSet1.designer.vb (cs) file.
The next class it's the row definition. Just copy-paste them into a new class file.
If you want a more complete datatable object, the next class below
the row class define events, and the delegate it's just above the
table def.
Simple and I tested it to work in conjunction of the remaining program, that uses untyped.
Perhaps it would be like polishing a turd, but I would like to add data annotations somewhere to do some client validations like in EF. And perhaps replace the columns constructor parameters for them. (but I caaan't)
good Luck.
I have a database "Pubs" with a table "authors". I have made a dbml file from the database by dragging over "authors".
Here is the "Default.aspx.vb"
Public Class _Default
Inherits System.Web.UI.Page
Dim author As Object
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim db As New PubsContext
Dim authors = From p In dbo.authors _
Select p
GridView1.DataSource = author
GridView1.DataBind()
End Sub
End Class
Here is the class for it: "Class1.vb"
Partial Public Class PubsContext
Dim authors As Object
Public Function GetProductsByCategory(ByVal id1 As Integer) As IEnumerable(Of authors)
Return From p In Me.authors _
Where p.au_id = id1 _
Select p
End Function
End Class
Error code:
"Expression of type 'Object' is not queryable. Make sure you are not missing an assembly reference and/or namespace import for the LINQ".
In references there is already a "System.Data.Linq". What should I do?
Well this is the problem:
Dim authors As Object
That's just an object. What does it mean to call Select, Where etc on that? Where are you even giving it a value? Work out what the type should really be, make sure you give it an appropriate value to start with, and you should be fine.
It's not clear why you're introducing your own authors field at all, to be honest - I'd expect the generated context to have an Authors property of type Table<Author> or something similar.
(I note that you're also trying to set GridView1.DataSource to author rather than authors, by the way... Why are you doing that? What value are you expecting the author field in _Default to have?)