Key not valid for use in specified state

The following worked for me:

From the main taskbar in VS 2005, go to View|Other Windows|Server Explorer.

Select your existing Data Connections.

Delete the bad data connection (or ALL of them) in Server Explorer, and recreate them in Server Explorer.

Các kiểu dữ liệu của SQL & VB

Các kiểu dữ liệu cơ sở :

SQL

Data Types	Description
bigint	Integer data from -2^63 through 2^63-1
int	Integer data from -2^31 through 2^31 - 1
smallint	Integer data from -2^15 through 2^15 - 1
tinyint	Integer data from 0 through 255
bit	Integer data with either a 1 or 0 value
decimal	Fixed precision and scale numeric data from -10^38 +1 through 10^38 -1
numeric	Fixed precision and scale numeric data from -10^38 +1 through 10^38 -1
money	Monetary data values from -2^63 through 2^63 - 1
smallmoney	Monetary data values from -214,748.3648 through +214,748.3647
float	Floating precision number data from -1.79E + 308 through 1.79E + 308
real	Floating precision number data from -3.40E + 38 through 3.40E + 38
datetime	Date and time data from January 1, 1753, through December 31, 9999, with an accuracy of 3.33 milliseconds
smalldatetime	Date and time data from January 1, 1900, through June 6, 2079, with an accuracy of one minute
char	Fixed-length character data with a maximum length of 8,000 characters
varchar	Variable-length data with a maximum of 8,000 characters
text	Variable-length data with a maximum length of 2^31 - 1 characters
nchar	Fixed-length Unicode data with a maximum length of 4,000 characters
nvarchar	Variable-length Unicode data with a maximum length of 4,000 characters
ntext	Variable-length Unicode data with a maximum length of 2^30 - 1 characters
binary	Fixed-length binary data with a maximum length of 8,000 bytes
varbinary	Variable-length binary data with a maximum length of 8,000 bytes
image	Variable-length binary data with a maximum length of 2^31 - 1 bytes
cursor	A reference to a cursor
sql_variant	A data type that stores values of various data types, except text, ntext, timestamp, and sql_variant
table	A special data type used to store a result set for later processing
timestamp	A database-wide unique number that gets updated every time a row gets updated
uniqueidentifier	A globally unique identifier

Visual Basic

Kiểu dữ liệu	Mô tả
Boolean	Gồm 2 giá trị: TRUE & FALSE.
Byte	Các giá trị số nguyên từ 0 – 255
Integer	Các giá trị số nguyên từ -32768 – 32767
Long	Các giá trị số nguyên từ -2147483648 – 2147483647. Kiểu dữ liệu này thường được gọi là số nguyên dài.
Single	Các giá trị số thực từ -3.402823E+38 – 3.402823E+38. Kiểu dữ liệu này còn được gọi là độ chính xác đơn.
Double	Các giá trị số thực từ -1.79769313486232E+308 - 1.79769313486232E+308. Kiểu dữ liệu này được gọi là độ chính xác kép.
Currency	Dữ liệu tiền tệ chứa các giá trị số từ -922.337.203.685.477,5808 - 922.337.203.685.477,5807.
String	Chuỗi dữ liệu từ 0 đến 65.500 ký tự hay ký số, thậm chí là các giá trị đặc biệt như ^%@. Giá trị kiểu chuỗi được đặt giữa 2 dấu ngoặc kép (“”).
Date	Dữ liệu kiểu ngày tháng, giá trị được đặt giữa cặp dấu ##. Việc định dạng hiển thị tùy thuộc vào việc thiết lập trong Control Panel.
Variant	Chứa mọi giá trị của các kiểu dữ liệu khác, kể cả mảng.

Lấy User ID từ Data Access Layer

Iron Speed Designer maintains strict separation of the user interface layer from the Data Access Layer. For example, the currently logged in user is not available directly in the Data Access Layer. In some cases our users have asked to use this information even in the Data Access Layer.

You can access the user information from the session in the Data Access Layer. Use the fully specified session class to get access to this information.

System.Web.HttpContext.Current.Session

For example:

Dim sessionData As System.Collections.Hashtable

sessionData = CType(System.Web.HttpContext.Current.Session.Item( _

BaseClasses.Utils.SessionConst.LoginInfo), _

Hashtable)

Then you can use the following to get the variables:

CStr(sessionData(BaseClasses.Utils.SessionConst.UserId))

CStr(sessionData(BaseClasses.Utils.SessionConst.UserName))

CStr(sessionData(BaseClasses.Utils.SessionConst.UserTable))

CStr(sessionData(BaseClasses.Utils.SessionConst.UserRole))

For example, you can do something like the following:

Dim EmailContent As String = “The current user is: ” & _

CStr(sessionData(BaseClasses.Utils.SessionConst.UserName))

Source: http://www.ironspeed.com

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.

Solution:

1. I have had alot of issues with Visual Studio 2005 and Crystal Reports and this was one of them. You can avoid the error by setting the EnforceConstraints property of your DataSet to False
_SubDataSet2.EnforceConstraints = False

Also if you are using an .xsd file, check the properties and make sure the AllowDBNull property is set to False.

2. Check all the MaxLength property of the columns in your DataTable.

The column that I changed from "nvarchar(512)" to "nvarchar(MAX)" still had the 512 value on the MaxLength property so I changed to "-1" and it works!!.

Hope this helps!

Code lấy ngày đầu và ngày cuối cùng của 1 tháng

Dim Calendar As New System.Globalization.GregorianCalendar()

'Ngày đầu tiên của tháng lúc nào cũng là ngày 1
Dim firstDayOfMonth As New DateTime(DateTime.Now.Year, DateTime.Now.Month, 1)

'Lấy ngày cuối cùng của tháng
Dim lastDayOfMonth As New DateTime(DateTime.Now.Year, DateTime.Now.Month, Calendar.GetDaysInMonth(DateTime.Now.Year, DateTime.Now.Month))

Getting Configuration Parameters from app.config

How to get a configuration parameter from app.config
Visual Basic 2005 (vb.net)

Visual Basic automatically makes an app.config file in the root folder of your application. This is true for C# too. This file contains all sorts of configuration parameters that VB uses, as well as any custom ones that you care to define.
One very useful parameter is the Connection String that is used to connect to a SQL Server or MS Access database. This parameter is simply called ConnectionString.
If you want to read any of these configuration parameters from the app.config file at runtime, you need to do the following:

1. Add a reference to System.Configuration to the reference section of your project. (Look for it in Solution Explorer.)

2. Insert the statement:
imports system.configuration
at the top of your VB code file.

3. Then to access the parameter, use this:
Dim connectionString As String = System.Configuration.ConfigurationManager.ConnectionStrings( "myConnectionString").ConnectionString

Your app.config file is just some XML,...........

As another tip, if you have multiple configuration strings, sometimes referring to them by name can be a pain, so you can refer to them by number instead, using 0 as the first one, 1 as the second, etc:
System.Configuration.ConfigurationManager.ConnectionStrings( 0).ConnectionString

Select DISTINCT on DataTable

Public Shared Function SelectDistinct(ByVal SourceTable As DataTable, ByVal ParamArray FieldNames() As String) As DataTable
Dim lastValues() As Object
Dim newTable As DataTable

If FieldNames Is Nothing OrElse FieldNames.Length = 0 Then
Throw New ArgumentNullException("FieldNames")
End If

lastValues = New Object(FieldNames.Length - 1) {}
newTable = New DataTable

For Each field As String In FieldNames
newTable.Columns.Add(field, SourceTable.Columns(field).DataType)
Next

For Each Row As DataRow In SourceTable.Select("", String.Join(", ", FieldNames))
If Not fieldValuesAreEqual(lastValues, Row, FieldNames) Then
newTable.Rows.Add(createRowClone(Row, newTable.NewRow(), FieldNames))

setLastValues(lastValues, Row, FieldNames)
End If
Next

Return newTable
End Function

Private Shared Function fieldValuesAreEqual(ByVal lastValues() As Object, ByVal currentRow As DataRow, ByVal fieldNames() As String) As Boolean
Dim areEqual As Boolean = True

For i As Integer = 0 To fieldNames.Length - 1
If lastValues(i) Is Nothing OrElse Not lastValues(i).Equals(currentRow(fieldNames(i))) Then
areEqual = False
Exit For
End If
Next

Return areEqual
End Function

Private Shared Function createRowClone(ByVal sourceRow As DataRow, ByVal newRow As DataRow, ByVal fieldNames() As String) As DataRow
For Each field As String In fieldNames
newRow(field) = sourceRow(field)
Next

Return newRow
End Function

Private Shared Sub setLastValues(ByVal lastValues() As Object, ByVal sourceRow As DataRow, ByVal fieldNames() As String)
For i As Integer = 0 To fieldNames.Length - 1
lastValues(i) = sourceRow(fieldNames(i))
Next
End Sub

VB.NET 2005

Xem các phim minh họa về VB.NET . Sau khi xem các phim này xong, xem như bài tập cơ bản và bài tập nâng cao về VB.NET 2005. Thực hành y theo các phim hướng dẫn này

1. Tạo giao diện VB.Net 2005
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/02%20-%20VB.wmv

2. Bắt sự kiện trong VB.Net 2005
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/03%20-%20VB.wmv

3. Sử dụng biến trong VB.Net 2005
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/04VB.wmv

4. Cấu trúc rẽ nhánh
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/05VB.wmv

5. Lập trình hướng đối tượng trong VB.Net 2005

http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/06VB1.wmv
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/06VB2.wmv

6. Truy cập data với SQL Server trong VB.Net 2005
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/08VB.wmv

7.Data Bindind: hiển thị dữ liệu trong VB.Net 2005
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/09VB.wmv

8.Bẫy lỗi trong VB.Net 2005
http://download.microsoft.com/download/6/2/4/6247616D-A0C7-4552-B622-3F0450DE2462/11VB.wmv

9. Chơi nhạc - pim trong VB.Net 2005
http://download.microsoft.com/download/4/1/e/41e8f2c1-1bf7-419f-b31b-06122d090a49/AudioPart1VB.msi
http://download.microsoft.com/download/4/1/e/41e8f2c1-1bf7-419f-b31b-06122d090a49/AudioPart2VB.msi

10.Tăng cường giao diện trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/ButtonCustomizeVB.wvx

11. Sử dụng Dialog Controls trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/DialogControlsVB.wvx

12. Sử dụng FlowLayout Panel trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/FlowLayoutPanelVB.wvx

13. SysTray trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/NotifyIconVB.wvx

14. sử dụng SPlit control trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/SplitContainerVB.wvx

15. TableLayout trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/TableLayoutPanelVB.wvx

16. Sử dụng Timer trong VB.Net 2005
http://msdn.microsoft.com/vstudio/express/media/en/vb/TimerControlVB.wvx