The DataColumnMapping.SourceColumn is required to be unique. 'ColumnName' already exists in the collection.

Problem:

While configuring Table Adapter query in ADO.Net Dataset, you may have received this error:

 The DataColumnMapping.SourceColumn is required to be unique. 'Column' already exists in the collection. 

Solution:

Open the Dataset's xsd file with XML text editor. Search for the column name showing in the error. Manually remove the mapping column and then save the xml file.

Hopefully you will have no error from now on.

Add-Migration : The term 'Add-Migration' is not recognized as the name of a cmdlet...

Problem

Add-Migration : The term 'Add-Migration' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

Solution

1. Open Menu Nuget Package Manager > Manage Nuget Packages for Solution
2. If you are using EFCore then, Browse Package Microsoft.EntityFrameworkCore.Tools
3. If you are using EntityFramework then, Browse Package Microsoft.EntityFramework.Tools
4. Instal the Package
5. Run the command again : add-migration initial

Hope your problem will be solved.

VirtualBox Error during Installation: Failed to retreive the preconfiguration file.

Problem:

While Installing Raspberry Pi over VirtualBox, you may encounter the following error:

Load debconf preconfiguration file.

The file needed for preconfiguration could not be retreived from....blah, blah, blah... The installation will proceed in non-automated mode.

Solution:

The installation file (Disk image) might be corrupt. Re-download the image from the official site, hopefully your problem will be resolved.

I would love to hear from you. Happy coding!

ORA-00604: error occurred at recursive SQL level 1 ORA-12705: Cannot access NLS data files or invalid environment specified 00604. 00000

Problem:

While connecting to an Oracle database with SQL Developer or JDeveloper, you might got this error:

Error:

An error was encountered performing the requested operation:
ORA-00604: error occurred at recursive SQL level 1
ORA-12705: Cannot access NLS data files or invalid environment specified 00604. 00000 -  "error occurred at recursive SQL level %s"

*Cause:    An error occurred while processing a recursive SQL statement            (a statement applying to internal dictionary tables).

*Action:   If the situation described in the next error on the stack            can be corrected, do so; otherwise contact Oracle Support. Vendor code 604

Solution:

The solution for this problem is simple, but I had to go through a number of websites to find its solution. So here it is:

1. If you are using SQL Developer:

Goto SQL Developer directory and there will be another SQL Developer directory, open it. Open bin folder, and you will find sqldeveloper.conf file in it.

Add 2 entries in sqldevelper.conf file:

AddVMOption -Duser.language=en
AddVMOption -Duser.region=US

Save the file and reopen SQL developer application, connect the database. Hope it will resolve your problem.

2. For JDeveloper, you have to perform the same procedure as described in (1), but in jdev.conf file.

Windows Update not working on newly installed Windows system.

Hi All,

You may experience this type of problem, where windows update was not working. You can follow below steps to ensure everything is correct and on its way.

1. First of all, check all Services related to Windows Update, like Windows Update Service, Cryptographic, BITS etc, are running.

2. Secondly, make sure your internet is properly working and you are able to browse windows update website in your browser. (http://www.update.microsoft.com/windowsupdate/)

3. Make sure you have installed all the latest drivers on your PC/Laptop, especially Operating System enhancements drivers, etc. This is an important step because it can prevent Windows Update from downloading updates.

4. Check the Software Distribution folder, whether it has the downloaded updates. The folder must be present in Windows directory.

5. If the downloaded updates are there, then check the Update History, available in Windows Update form.

6. Also check the WindowsUpdate.log file in Windows directory for errors. If there is an error in the log, try to search this error on the internet.

7. If log error shows error code : 8009017, then go to this microsoft page and reset Windows Update components by following the steps written there.

I hope this post will help you resolve the Windows Update problems. Must tell me the results by commenting on the blog.

Have a nice day.

God Bless.

Configure Office 365 Email on Android Mobile App

While Office 365 does not officially support open source mail clients, this article will provide you with settings that may help you set up your mail client to access Office 365 Exchange.

If your email client supports Exchange Web Services (EWS), use the following settings:

Field	Value
Email Address	(YOUR EMAIL ADDRESS)
Username	(YOUR EMAIL ADDRESS)
Domain	Leave Blank
Exchange Server	outlook.office365.com
Server Address	https://outlook.office365.com
EWS Server	https://outlook.office365.com/ews/exchange.asmx
Outlook Web Access	https://outlook.office365.com

If your email client does not support Exchange Web Services (EWS), you will need to configure your client to use traditional POP/IMAP + SMTP. Use the following settings:

User Settings:

Email Address	(YOUR EMAIL ADDRESS)
Username	(YOUR EMAIL ADDRESS)

Inbound Servers:

Type	Server Address	Port
POP Server (SSL)	outlook.office365.com	995
IMAP Server (SSL)	outlook.office365.com	993

Outbound Servers:

Type	Server Address	Port
SMTP Server (SSL)	smtp.office365.com	587

Unexpected Error occurred in the Oracle Data Provider for .NET

While working with Oracle Data Provider with Visual studio you can get the following error:

The description for Event ID 0 from source devenv cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.
If the event originated on another computer, the display information had to be saved with the event.
The following information was included with the event:
An unexpected error occurred in the Oracle Data Provider for .NET.  The data provider 'Oracle Data Provider for .NET' failed to load.  The {18147ff9-1f37-4425-865b-5066a33701de} service could not be found.
the message resource is present but the message is not found in the string/message table

Solution:

The simple solution to this problem is to check your "Server Explorer" in Visual Studio, remove all connections, and then restart Visual studio.

Hopefully your problem will be solved.