Developing a Database Execution Policies in Entity Framework Core 6

We were developing a database project in .NET 6 using Entity Framework Core. Our back-end database engine was MySql rather than SQL server. It was a remote database. Short operations like single read and write worked fine but suddenly I stuck somewhere and got this horrible error.

The error was

“A second operation was started on this context instance before a previous operation was completed. This is usually caused by different threads concurrently using the same instance of DbContext.”

I started the operation again and surprisingly, this time the error was different regardless of the fact that all the inputs I provided were the same.

The error I got this time is:

“ The configured execution strategy 'MySqlRetryingExecutionStrategy' does not support user-initiated transactions. Use the execution strategy returned by 'DbContext.Database.CreateExecutionStrategy()' to execute all the operations in the transaction as a retriable unit.' ”

Please note that if you are using SQL Server as a database engine, You’ll receive SqlRetryingExecutionStrategy rather than MySqlRetryingExecutionStrategy.

I tested the application many times and explored the stack trace in detail and also do a lot of search online but failed to figure out the issue as my app followed all the suggested solution standards.

I started following a thread on github where one important thing was mentioned.

One has to be careful while working with sync and async method. If you are following sync method patterns in your code, better to follow it completely, mean use sync method in all of your codebase. Don’t mix sync calls with async calls in your code.

If you working with async methods in your code it is highly recommended to use the async method with await in all the places in your codebase.

This last line give me some hint to find out the issue so started exploring the code backward. From the position where error or exception was coming while going backward from line to line, there was an async function which has no await before its invocation.

As soon as I applied this await prior to this call, both errors are gone.

Original article source at: https://www.c-sharpcorner.com/

#database #core #csharp 

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PySQL Tutorial: A Database Framework for Python

PySQL 

PySQL is database framework for Python (v3.x) Language, Which is based on Python module mysql.connector, this module can help you to make your code more short and more easier. Before using this framework you must have knowledge about list, tuple, set, dictionary because all codes are designed using it. It's totally free and open source.

Tutorial Video in English (Watch Now)

Installation

Before we said that this framework is based on mysql.connector so you have to install mysql.connector first on your system. Then you can import pysql and enjoy coding!

python -m pip install mysql-connector-python

After Install mysql.connector successfully create Python file download/install pysql on the same dir where you want to create program. You can clone is using git or npm command, and you can also downlaod manually from repository site.

PyPi Command

Go to https://pypi.org/project/pysql-framework/ or use command

pip install pysql-framework

Git Command

git clone https://github.com/rohit-chouhan/pysql

Npm Command

Go to https://www.npmjs.com/package/pysql or use command

$ npm i pysql

Snippet Extention for VS Code

Install From Here https://marketplace.visualstudio.com/items?itemName=rohit-chouhan.pysql

Table of contents

• Connecting a Server
• Create a Database in Server
• Drop Database
• Connecting a Database
• Creating Table in Database
• Drop Table in Database
• Selecting data from Table
• Add New Column to Table
• Modify Column to Table
• Drop Column from Table
• Manual Execute Query
• Inserting data
• Updating data
• Deleting data

Connecting a Server

---

To connect a database with localhost server or phpmyadmin, use connect method to establish your python with database server.

import pysql

db = pysql.connect(
    "host",
    "username",
    "password"
 )

Create a Database in Server

---

Creating database in server, to use this method

import pysql

db = pysql.connect(
    "host",
    "username",
    "password"
 )
 pysql.createDb(db,"demo")
 #execute: CREATE DATABASE demo

Drop Database

---

To drop database use this method .

Syntex Code -

pysql.dropDb([connect_obj,"table_name"])

Example Code -

pysql.dropDb([db,"demo"])
#execute:DROP DATABASE demo

Connecting a Database

---

To connect a database with localhost server or phpmyadmin, use connect method to establish your python with database server.

import pysql

db = pysql.connect(
    "host",
    "username",
    "password",
    "database"
 )

Creating Table in Database

---

To create table in database use this method to pass column name as key and data type as value.

Syntex Code -

pysql.createTable([db,"table_name_to_create"],{
    "column_name":"data_type", 
    "column_name":"data_type"
})

Example Code -

pysql.createTable([db,"details"],{
    "id":"int(11) primary", 
     "name":"text", 
    "email":"varchar(50)",
    "address":"varchar(500)"
})

2nd Example Code -

Use can use any Constraint with Data Value

pysql.createTable([db,"details"],{
    "id":"int NOT NULL PRIMARY KEY", 
     "name":"varchar(20) NOT NULL", 
    "email":"varchar(50)",
    "address":"varchar(500)"
})

Drop Table in Database

---

To drop table in database use this method .

Syntex Code -

pysql.dropTable([connect_obj,"table_name"])

Example Code -

pysql.dropTable([db,"users"])
#execute:DROP TABLE users

Selecting data from Table

---

For Select data from table, you have to mention the connector object with table name. pass column names in set.

Syntex For All Data (*)-

records = pysql.selectAll([db,"table_name"])
for x in records:
  print(x)

Example - -

records = pysql.selectAll([db,"details"])
for x in records:
  print(x)
#execute: SELECT * FROM details

Syntex For Specific Column-

records = pysql.select([db,"table_name"],{"column","column"})
for x in records:
  print(x)

Example - -

records = pysql.select([db,"details"],{"name","email"})
for x in records:
  print(x)
#execute: SELECT name, email FROM details

Syntex Where and Where Not-

#For Where Column=Data
records = pysql.selectWhere([db,"table_name"],{"column","column"},("column","data"))

#For Where Not Column=Data (use ! with column)
records = pysql.selectWhere([db,"table_name"],{"column","column"},("column!","data"))
for x in records:
  print(x)

Example - -

records = pysql.selectWhere([db,"details"],{"name","email"},("county","india"))
for x in records:
  print(x)
#execute: SELECT name, email FROM details WHERE country='india'

Add New Column to Table

---

To add column in table, use this method to pass column name as key and data type as value. Note: you can only add one column only one call

Syntex Code -

pysql.addColumn([db,"table_name"],{
    "column_name":"data_type"
})

Example Code -

pysql.addColumn([db,"details"],{
    "email":"varchar(50)"
})
#execute: ALTER TABLE details ADD email varchar(50);

Modify Column to Table

---

To modify data type of column table, use this method to pass column name as key and data type as value.

Syntex Code -

pysql.modifyColumn([db,"table_name"],{
    "column_name":"new_data_type"
})

Example Code -

pysql.modifyColumn([db,"details"],{
    "email":"text"
})
#execute: ALTER TABLE details MODIFY COLUMN email text;

Drop Column from Table

---

Note: you can only add one column only one call

Syntex Code -

pysql.dropColumn([db,"table_name"],"column_name")

Example Code -

pysql.dropColumn([db,"details"],"name")
#execute: ALTER TABLE details DROP COLUMN name

Manual Execute Query

---

To execute manual SQL Query to use this method.

Syntex Code -

pysql.query(connector_object,your_query)

Example Code -

pysql.query(db,"INSERT INTO users (name) VALUES ('Rohit')")

Inserting data

---

For Inserting data in database, you have to mention the connector object with table name, and data as sets.

Syntex -

data =     {
    "db_column":"Data for Insert",
    "db_column":"Data for Insert"
}
pysql.insert([db,"table_name"],data)

Example Code -

data =     {
    "name":"Komal Sharma",
    "contry":"India"
}
pysql.insert([db,"users"],data)

Updating data

---

For Update data in database, you have to mention the connector object with table name, and data as tuple.

Syntex For Updating All Data-

data = ("column","data to update")
pysql.updateAll([db,"users"],data)

Example - -

data = ("name","Rohit")
pysql.updateAll([db,"users"],data)
#execute: UPDATE users SET name='Rohit'

Syntex For Updating Data (Where and Where Not)-

data = ("column","data to update")
#For Where Column=Data
where = ("column","data")

#For Where Not Column=Data (use ! with column)
where = ("column!","data")
pysql.update([db,"users"],data,where)

Example -

data = ("name","Rohit")
where = ("id",1)
pysql.update([db,"users"],data,where)
#execute: UPDATE users SET name='Rohit' WHERE id=1

Deleting data

---

For Delete data in database, you have to mention the connector object with table name.

Syntex For Delete All Data-

pysql.deleteAll([db,"table_name"])

Example - -

pysql.deleteAll([db,"users"])
#execute: DELETE FROM users

Syntex For Deleting Data (Where and Where Not)-

where = ("column","data")

pysql.delete([db,"table_name"],where)

Example -

#For Where Column=Data
where = ("id",1)

#For Where Not Column=Data (use ! with column)
where = ("id!",1)
pysql.delete([db,"users"],where)
#execute: DELETE FROM users WHERE id=1

--- Finish ---

Change Logs

[19/06/2021]
 - ConnectSever() removed and merged to Connect()
 - deleteAll() [Fixed]
 - dropTable() [Added]
 - dropDb() [Added]
 
[20/06/2021]
 - Where Not Docs [Added]

The module is designed by Rohit Chouhan, contact us for any bug report, feature or business inquiry.

Author: rohit-chouhan
Source Code: https://github.com/rohit-chouhan/pysql
License: Apache-2.0 License

#python 

Best Android Mobile App Development Frameworks

Are you looking for the best Android app development frameworks? Get the best Android app development frameworks that help to build the top-notch Android mobile app.

For more info:
Website: https://www.appcluesinfotech.com/
Email: info@appcluesinfotech.com
Call: +1-978-309-9910

#best android mobile app development frameworks #top mobile app development frameworks #android app development frameworks #top frameworks for android app development #most popular android app development frameworks #app development frameworks

jQuery Ajax CRUD in ASP.NET Core MVC with Modal Popup

In this article, we’ll discuss how to use jQuery Ajax for ASP.NET Core MVC CRUD Operations using Bootstrap Modal. With jQuery Ajax, we can make HTTP request to controller action methods without reloading the entire page, like a single page application.

To demonstrate CRUD operations – insert, update, delete and retrieve, the project will be dealing with details of a normal bank transaction. GitHub repository for this demo project : https://bit.ly/33KTJAu.

Sub-topics discussed :

• Form design for insert and update operation.
• Display forms in modal popup dialog.
• Form post using jQuery Ajax.
• Implement MVC CRUD operations with jQuery Ajax.
• Loading spinner in .NET Core MVC.
• Prevent direct access to MVC action method.

Create ASP.NET Core MVC Project

In Visual Studio 2019, Go to File > New > Project (Ctrl + Shift + N).

From new project window, Select Asp.Net Core Web Application_._

Once you provide the project name and location. Select Web Application(Model-View-Controller) and uncheck HTTPS Configuration. Above steps will create a brand new ASP.NET Core MVC project.

Setup a Database

Let’s create a database for this application using Entity Framework Core. For that we’ve to install corresponding NuGet Packages. Right click on project from solution explorer, select Manage NuGet Packages_,_ From browse tab, install following 3 packages.

Now let’s define DB model class file – /Models/TransactionModel.cs.

public class TransactionModel
{
    [Key]
    public int TransactionId { get; set; }

    [Column(TypeName ="nvarchar(12)")]
    [DisplayName("Account Number")]
    [Required(ErrorMessage ="This Field is required.")]
    [MaxLength(12,ErrorMessage ="Maximum 12 characters only")]
    public string AccountNumber { get; set; }

    [Column(TypeName ="nvarchar(100)")]
    [DisplayName("Beneficiary Name")]
    [Required(ErrorMessage = "This Field is required.")]
    public string BeneficiaryName { get; set; }

    [Column(TypeName ="nvarchar(100)")]
    [DisplayName("Bank Name")]
    [Required(ErrorMessage = "This Field is required.")]
    public string BankName { get; set; }

    [Column(TypeName ="nvarchar(11)")]
    [DisplayName("SWIFT Code")]
    [Required(ErrorMessage = "This Field is required.")]
    [MaxLength(11)]
    public string SWIFTCode { get; set; }

    [DisplayName("Amount")]
    [Required(ErrorMessage = "This Field is required.")]
    public int Amount { get; set; }

    [DisplayFormat(DataFormatString = "{0:MM/dd/yyyy}")]
    public DateTime Date { get; set; }
}

C#Copy

Here we’ve defined model properties for the transaction with proper validation. Now let’s define  DbContextclass for EF Core.

#asp.net core article #asp.net core #add loading spinner in asp.net core #asp.net core crud without reloading #asp.net core jquery ajax form #asp.net core modal dialog #asp.net core mvc crud using jquery ajax #asp.net core mvc with jquery and ajax #asp.net core popup window #bootstrap modal popup in asp.net core mvc. bootstrap modal popup in asp.net core #delete and viewall in asp.net core #jquery ajax - insert #jquery ajax form post #modal popup dialog in asp.net core #no direct access action method #update #validation in modal popup

Announcing Entity Framework Core (EF Core) 5 RC2

Today, the Entity Framework Core team announces the second release candidate (RC2) of EF Core 5.0. This is a feature complete release candidate of EF Core 5.0 and ships with a “go live” license. You are supported using it in production. This is a great opportunity to start using EF Core 5.0 early while there is still time to fix remaining issues. We’re looking for reports of any remaining critical bugs that should be fixed before the final release.

Prerequisites

EF Core 5.0 will not run on .NET Standard 2.0 platforms, including .NET Framework.

• The release candidates of EF Core 5.0 require .NET Standard 2.1.
• This means that EF Core 5.0 will run on .NET Core 3.1 and does not require .NET 5.
• To summarize: EF Core 5.0 runs on platforms that support .NET Standard 2.1.

How to get EF Core 5.0 Release Candidate 2

EF Core is distributed exclusively as a set of NuGet packages. For example, to add the SQL Server provider to your project, you can use the following command using the dotnet tool:

dotnet add package Microsoft.EntityFrameworkCore.SqlServer --version 5.0.0-rc.2.20475.6

#.net #.net core #.net framework #asp.net #c# #entity framework #announcement #asp.net core #entity framework core

Entity Framework Core in ASP.NET Core 3.1

This article will be covering in detail the implementation of Entity Framework Core in ASP.NET Core Web API. We will learn about entity framework core in details i.e. what, how & why and see how to use it in ASP.NET Core Web API to implement CRUD operations. Though here we will be using entity framework in ASP.NET Core this can be implemented even in .NET Framework for your data persistence. I hope you will join me on this and go through step by step demonstration on implementing entity framework core in ASP.NET Core Web API.

Introduction to Entity Framework Core

Entity Framework has been around since 2008 which has improved over the years. Entity framework core was introduced for .NET Core based applications. It is an open-source object-relational mapper (ORM) built over ADO.NET and an official data access platform from Microsoft. Entity framework core has been rewritten from scratch to make it lightweight, flexible & achieve better performance.

In the absence of an ORM typically lots of code have to be written to perform CRUD operations with the database. using an ORM like entity framework can reduce the number of lines of code to be written for database interactions. Typical ORM will work on classes & database tables of similar structure but entity framework core implements mappings which makes it a lot more flexible i.e. in case table & class does not match then mappings can be exercised to get from objects to tables.

Entity framework core can work with wide variety of databases. Microsoft provides rich providers for SQL Server & SQLite and there are many other third party providers some commercial and some from community.

How does entity framework core works?

1. Define domain classes & configure entity framework DbContext API along with mappings to let entity framework work how this class maps to the database schema.
2. Write LINQ to objects to fetch data from the database.
3. Based on mappings & database provider configured entity framework will translate queries into SQL that’s understood by the database.
4. The query is executed and the object is populated with data.
5. Data in objects can be modified, deleted or new records can be added to the list & once done call DbContext.saveChanges from EF API to save data back to the database.
6. The entity framework will generate the required SQL statements to save data back to the database.

#programming #.net core #asp.net core 3.1 #entity framework #entity framework core