Enable .NET Core Entity Framework Linq query execution

When we create a new .NET Core class it only contains the using System; reference.

To enable Linq database queries in a .NET Core project, add using System.Linq;

using System;
using System.Linq;

To enable the usage of .Include() in the Linq queries, add

using Microsoft.EntityFrameworkCore;

 

Procedure or function ‘`…_Insert`’ cannot be found in database …

When you use the Microsoft .NET Entity framework to access a MySql database, the autogenerated code throws an error when you try to insert a row into the database with

context.MY_TABLE.Add(MY_OBJECT);

Server Error in ‘/’ Application.
Procedure or function ‘`…_Insert`’ cannot be found in database ‘`…`’.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: MySql.Data.MySqlClient.MySqlException: Procedure or function ‘`…_Insert`’ cannot be found in database ‘`…`’.

The auto-generated class tries to use stored procedures to update the database. To use the Entity Framework Linq commands, comment out the line that contains “MapToStoredProcedures”

 protected override void OnModelCreating(DbModelBuilder modelBuilder)
 {
     base.OnModelCreating(modelBuilder);
     // modelBuilder.Entity<twitter_keywords>().MapToStoredProcedures();
 }

 

 

No connection string named ‘…’ could be found in the application config file.

Two-tier applications separate the presentation layer and the data layer, and all database access related objects are located in the data-tier.

When the application runs, the config file of the main project is read. In web applications, it is the web.config, in console applications the app.config file.

When you get the following runtime exception

Exception thrown: ‘System.InvalidOperationException’ in EntityFramework.dll
An exception of type ‘System.InvalidOperationException’ occurred in EntityFramework.dll but was not handled in user code
No connection string named ‘…Entities’ could be found in the application config file.

 

  1. Copy the connection string from the app.config file of the data-tier to the main project’s config file.
 <add name="USC_SocialMediaMSSQLEntities" connectionString="metadata=res://*/USC_SocialMedia_MSSQL.csdl|res://*/USC_SocialMedia_MSSQL.ssdl|res://*/USC_SocialMedia_MSSQL.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=MY_SERVER;initial catalog=MY_DATABASE;user id=MY_USER;password=MY_PASWORD;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

2. This is a sample data access class in the data-layer to read data from the aspNetRoles table.

using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SocialMedia_Data {
	public class SocialMediaData {

		private USC_SocialMediaMSSQLEntities _web;

		public SocialMediaData() {

			// Set up the database connections
			_web = new USC_SocialMediaMSSQLEntities();

		}

		/// Returns the list of Roles
		public List GetRoles() {

			IEnumerable foundRoles = from aspNetRoles in _web.AspNetRoles
						 orderby aspNetRoles.DisplayOrder
						 select aspNetRoles;

			if (null == foundRoles || 0 == foundRoles.Count()) {
				return null;
			}

			return foundRoles.ToList();

		}
	}
}

NotSupportedException: Unable to determine the provider name for provider factory of type ‘MySql.Data.MySqlClient.MySqlClientFactory’. Make sure that the ADO.NET provider is installed or registered in the application config

In a two-tier web application, the data layer is in a separate project. This allows better separation between the presentation layer and the data layer. This way you can reuse the data project in another application that targets the same database.

To access a MySql database you need to add the MySql.Data and MySql.Data.Entity NuGet packages to the data project.

When you develop a two-tier application that targets a MySql database you may get the runtime error

NotSupportedException: Unable to determine the provider name for provider factory of type ‘MySql.Data.MySqlClient.MySqlClientFactory’. Make sure that the ADO.NET provider is installed or registered in the application config.

Even if all database interaction is handled in the data project, and you added the MySql NuGet packages to it, you need to add the MySql.Data and MySql.Data.Entity NuGet packages to the web project too, because the Web.config file contains the connection string that includes the reference to MySql.Data.MySqlClient.

<add name="MY_CONNECTION_NAME" providerName="MySql.Data.MySqlClient" connectionString="server=localhost;port=3306;database=MY_DATABASE;uid=MY_USERNAME;password=MY_PASSWORD" />

At the time of writing do not use version 6.10.6.0 of the packages, it causes the error

Exception thrown: ‘System.TypeLoadException’ in mscorlib.dll
An exception of type ‘System.TypeLoadException’ occurred in mscorlib.dll but was not handled in user code
Inheritance security rules violated by type: ‘MySql.Data.MySqlClient.MySqlProviderServices’. Derived types must either match the security accessibility of the base type or be less accessible.

Until a new, corrected version is published, install version 6.9.11.0 of both packages in both projects.

For more information on how to connect to a MySql database from Visual Studio see Connect to a MySQL database from Visual Studio 2017

 

 

Connect to a MySQL database from Visual Studio 2017

As of today weI can connect to a MySQL database, but cannot generate the Entity Data Model from a MySQL database in Visual Studio 2017

To access a MySQL database from Visual Studio 2017

IMPORTANT: First install MySQL for Visual Studio, and after that install MySQL Connector/Net.

If MySQL Connector/Net is already installed on your workstation, uninstall it before installing MySQL for Visual Studio and reinstall MySQL Connector/Net.

Install MySQL for Visual Studio

Available version information is at https://dev.mysql.com/doc/visual-studio/en/visual-studio-intro.html

  1. Close all instances of Visual Studio,
  2. Download the installer from https://dev.mysql.com/downloads/windows/visualstudio/
  3. Start the installer
  4. Click the Complete button,
  5. If you select Typical, make sure the Visual Studio 2017 components are selected

 

Install the MySql Connector/Net the fully-managed ADO.NET driver for MySQL

  1. Download the installer from https://dev.mysql.com/downloads/connector/net/
  2. Download version 6.9.10, because version 6.10.5 throws the

    Inheritance security rules violated by type: ‘MySql.Data.Entity.MySqlEFConfiguration’. Derived types must either match the security accessibility of the base type or be less accessible

    error. More info at https://stackoverflow.com/questions/47227495/inheritance-security-rules-violated-by-type-mysql-data-entity-mysqlefconfigura

  3. Select version 6.9.10, your operating system and click the Download button
  4. If you don’t want to create an Oracle account, click the No thanks… link
  5. Start the downloaded installer
  6. Click the Complete button

Install the NuGet packages

Make sure to install the same version of the NuGet packages as the MySql Connector/Net

The specified Security Group and Parameter Group are not set in the RDS instance

If the Terraform apply execution times out during the RDS instance creation, the specified Security Group and Parameter Group is not set in the RDS instance.

The solution is to set the timeout in the aws_db_instance resource. When a multi-az RDS instance is launched from a snapshot, the process can take more than 55 minutes. The default value is 40 minutes.

resource "aws_db_instance" "default" {
...
  timeouts {
    create = "120m"
    delete = "120m"
  }
...
}

java.sql.SQLException: Incorrect string value: ‘\xF0\x9F\x96\xA4\xE2\x9C…’ for column

When your application tries to store 4-byte Unicode characters in a MySQL database you may get the error rmessage

java.sql.SQLException: Incorrect string value: ‘\x..\x..\x..\x..\x..\x…’ for column

 

To store 4-byte Unicode characters in MySQL you need

  • a modern version of the database engine, version 5.5 or later,
  • set the column collation to COLLATE utf8mb4_unicode_ci in the database,
  • configure MySQL to use utf8mb4 in the character columns.

 

To set the default character set and server settings to utf8mb4

  1. Open the C:\ProgramData\MySQL\MySQL Server 5.x\my.ini file
  2. Under [client] add
    default-character-set = utf8mb4
  3. Under [mysql] set the value to utf8mb4 in line
    default-character-set = utf8mb4
  4. Under [mysqld] set the value to utf8mb4 in line
    character-set-server = utf8mb4
  5. Under [mysqld] add the lines
    character-set-client-handshake = FALSE
    character-set-server = utf8mb4
    collation-server = utf8mb4_unicode_ci

Restart the MySQL server

  1. Restart the MySQL database server for the changes to take effect
  2. in MySQL Workbench reconnect the database.

Change the schema of an existing database

  1. In MySQL Workbench connect to the database server,
  2. Right-click the database and select Alter Schema,
  3. Set the collation to utf8mb4_unicode_ci collation
  4. Click the Appy button to save the changes,
  5. Click the Apply button again to confirm the instructions,
  6. Click the Finish button to execute the script.

To check the database settings execute the SQL query in MySQL Workbench

use MY_DATABASE_NAME;
SHOW VARIABLES WHERE Variable_name LIKE 'character\_set\_%' OR Variable_name LIKE 'collation%';

It should show

+--------------------------+--------------------+
| Variable_name            | Value              |
+--------------------------+--------------------+
| character_set_client     | utf8mb4            |
| character_set_connection | utf8mb4            |
| character_set_database   | utf8mb4            |
| character_set_filesystem | binary             |
| character_set_results    | utf8mb4            |
| character_set_server     | utf8mb4            |
| character_set_system     | utf8               |
| collation_connection     | utf8mb4_unicode_ci |
| collation_database       | utf8mb4_unicode_ci |
| collation_server         | utf8mb4_unicode_ci |
+--------------------------+--------------------+

Repair and optimize all tables

Make sure you execute the mysqlcheck command to repair and optimize all tables to avoid silent update errors

On Windows

"C:\Program Files\MySQL\MySQL Server 5.7\bin\mysqlcheck" -u root -p --auto-repair --optimize --all-databases

The utility makes it easy to execute the repair and optimize commands for every table

# For each table
REPAIR TABLE table_name;
OPTIMIZE TABLE table_name;

MySQL Installation

To install the MySQL database server, download the installer from https://dev.mysql.com/downloads/

  1. Download the MySQL Community Server from https://dev.mysql.com/downloads/
  2. On the Generally Available (GA) Releases tab select the operating system and click the Go to Download Page button,
  3. Click the Download button next to the web or offline installer,
  4. If you don’t want to register at Oracle, click the No thanks, just start my download link,

On Windows

Install the Visual C++ Redistributable Packages for Visual Studio 2013

  1. In your web browser navigate to https://www.microsoft.com/en-us/download/details.aspx?id=40784
  2. Download both 32 and 64-bit packages
  3. Install both packages. The 64-bit package requires a reboot after installation.

Install MySQL

  1. Execute the downloaded MySQL installer.

How to restore a Microsoft SQL database from backup with the Microsoft SQL Server Management Studio (MSSMS) user interface

There are multiple reasons to restore a database from backup. One of them can be disaster recovery, the other is to bring the production database to the developer machine. In both cases, the computer already has the old version of the database. In the new version of Microsoft SQL Server Management Studio (MSSMS) we cannot find the “Close connections” checkbox anymore, so we have to make sure all connections are closed, and we specify a unique database file name to restore the database to.

  1. On the developer machine close all instances of Visual Studio to close the open database connections,
  2. Close all Microsoft SQL Server Management Studio tabs that are connected to the database,
  3. Move the backup file to the C:\Temp folder. Microsoft SQL Server Management Studio cannot see it in your Downloads folder.
  4. Make sure your user account does not automatically connect to the database you want to restore:
    1. In Security, Logins right click your username and select Properties,
    2. Set the Default database to master
  5.  Disconnect from the database server:
    1.  Right-click the database server and select Disconnect,

  6. Connect to the database engine, but do not open the database you want to restore:
    1. Execute,
      USE Master
  7. Import the database from production with the user interface:
    1. Right-click the database and select Tasks, Restore, Files and Filegroups
    2. Select the From device radio button
    3. Click the button to select the backup file
    4. In the Select backup devices window click the Add button to select the file
    5. Navigate to the C:\Temp folder and select the database backup file
    6. Click the OK button
    7. In the Select the backup sets section select the Restore check box in the file row, and click Options on the left side,
    8. On the Options tab select the Overwrite existing database (WITH REPLACE) check box, and click the button to set the new unique database file name,
    9. Click OK to ignore the error message on the Locate Database Files – … message box
    10. Navigate to the current database file, click it, and append the date of the backup to the end of the file name to specify a unique data file name, and click OK,
    11. On the Restore Files and FileGroups window click the OK button to restore the database

Update the database to make it work at the new location

  1. On a development machine set the databases to Simple recovery mode, so the log files do not grow out of bound.
    ALTER DATABASE my_database SET RECOVERY SIMPLE;
  2. Delete and recreate the users in the restored database, because those have different internal IDs if the database was migrated from a different server
    USE my_database;
    GO
    spDropUser 'my_user', 'dbo'
    GO
    DROP SCHEMA my_user
    GO

    For some reason If I type DECLARE below, WordPress crashes. Please add the letter E to the end of the first word below.

    DECLAR @user_name varchar(50)
    SET @user_name = 'my_user'
    USE my_database; EXEC sp_grantdbaccess @user_name; EXEC sp_addrolemember @rolename = 'db_datareader', @membername = @user_name; EXEC sp_addrolemember @rolename = 'db_datawriter', @membername = @user_name; 
    GO

Migrate databases to and from AWS RDS instances

Amazon Web Services do not provide tools to migrate data to, from and between AWS RDS instances.

There is a free utility that can do the job.

SQL Server Management Studio (SSMS)

Install Microsoft SQL Server Management Studio (SSMS), because the utility uses libraries from it.

  1. Download the installer for free from https://msdn.microsoft.com/en-us/library/mt238290.aspx

SQL Azure Migration Wizard

Installation

  1. Download the SQL Azure Migration Wizard from http://sqlazuremw.codeplex.com/
  2. Unzip the downloaded ZIP file into a folder on your hard drive
  3. Create a shortcut in your Start Menu for SQLAzureMW.exe

Migrate a database

  1. Start the SQL Azure Migration Wizard by executing the SQLAzureMW.exe file
  2. Select Database in the Analyze / Migrate section and click Next

Connect to the source database

  1. On the Connect to Server page
    1. Enter the address of the database server
    2. Select SQL Server Authentication
    3. Enter the database owner login name and password
    4. If you keep Master DB selected, the next screen will show the list of databases to select from
    5. To save the username and password select Save Login Information
    6. Click Connect

  2. Select the database to connect to and click Next
  3. Leave Script all database objects selected and click Next
  4. On the Script Wizard Summary page click Next
  5. Click Yes to start the read process
  6. On the Results Summary page select Auto Scroll Display to see the scrolling results
  7. When the read is done click Next

Connect to the target database

  1. Enter the connection properties of the target database server
  2. Select the target database
    1. To migrate the data into a new database click the Create Database button
    2. On mirrored RDS instances we cannot drop and recreate databases. To migrate data into an existing database
      1. Use SQL Management Studio to drop the existing tables to avoid key conflicts
      2. Select the target database on this page
  3. Click Next
  4. Click Yes to start the write process
  5. When the write process is done click Exit