C ＃ operate with MySQL

1. install Mysql（ Online tutorials include ）

2. Create project webapi

3. quote dll Generally in （ install MySQL Some have no reference ：ASP.NET Connect MySQL database The detailed steps - wusir - Blog Garden ）：C:\Program Files (x86)\MySQL\MySQL Connector Net 8.0.23\Assemblies\v4.5.2\MySql.Data.dll

4. Code ：（ Connect -》 Inquire about -》 Format get MySql The data of ）

   public static void GetMySqlData()
        {
            MySqlConnection conn = null;// establish MySqlConnection class
            conn = new MySqlConnection("server=localhost;user id=root;password=123456;database=magessystemdb; pooling=true;");// Create connection string , Provide the necessary information to connect to the database
            conn.Open();// Connect to database
            if (conn.State.ToString() == "Open")// Check whether the connection is successful
            {
                Console.WriteLine(" Connect MySQL Database success ");

                //MySqlCommand cmd = new MySqlCommand("insert into use values(0,'hubuyu')", conn);// establish MySqlCommand class , And provide SQL sentence , And what to do MySqlConnection object
                //int n = cmd.ExecuteNonQuery();// perform SQL sentence , Operate on the connected database ,ExecuteNonQuery() Method cannot be used in a query statement
               // Console.WriteLine(" Number of rows affected ：" + n);// Check the return value , Is the number of rows affected

                MySqlCommand cmd = new MySqlCommand("select*from `use`", conn);
                int n = cmd.ExecuteNonQuery();
                Console.WriteLine(" Select a query method ：1 For the use of MySqlDataReader Class to query ,2 For the use of ADO.NET(MySqlDataAdapter,DataSet,DataTable class ) The query :");

                int s = 2;
                if (s == 1)
                {
                    MySqlDataReader dr;// If you want to use a query statement , Should be created first MySqlDataReader class , This is a ExecuteReader() Return type of method
                    dr = cmd.ExecuteReader();// Use ExecuteReader() Method to execute the query statement
                    while (dr.Read())// Use Read() Method to query the returned MySqlDataReader Data in object , The return value is true or false
                    {
                        Console.WriteLine(dr["Id"] + " " + dr["Name"]);// Output the queried data ,dr[" Field name "], The field name here corresponds to the field name in the table queried by the database
                    }
                    dr.Close();// The key step , Don't forget to close MySqlDataReader object ！！！！！
                }
                else if (s == 2)
                {
                    MySqlDataAdapter da = new MySqlDataAdapter(cmd);// The second query method , Use MySqlDataAdapter object
                    DataSet ds = new DataSet();// establish DataSet object
                    DataTable dt = new DataTable();// establish DataTable object
                    da.Fill(ds, "use");// call Fill Method execution SQL sentence , And save the query in DataSet In the object
                    dt = ds.Tables["use"];// After retrieving the database , The retrieved data is stored in DataTable In the object
                    for (int i = 0; i < dt.Rows.Count; i++)// Reading data
                    {
                        var Id = dt.Rows[i]["Id"].ToString();
                        var Name = dt.Rows[i]["Name"].ToString();

                        Console.WriteLine(dt.Rows[i]["Id"].ToString() + " " + dt.Rows[i]["Name"].ToString());
                    }
                }

            }
            else
            {
                Console.WriteLine(" The connection fails ");
            }
            conn.Close();// The key step , Don't forget to close the connection ！！！！！
        }

5. It can be combined in the later stage SQL Statements are dynamically generated and mapped into entity classes

6. In this way, you can operate MySql Database

7. Pit encountered ：MySql.Data The version of should correspond to the corresponding .net Framework Corresponding ：Mysql 8.0.23 Corresponding .net 4.7.2

8.MySql Tools ：https://download.csdn.net/download/weixin_42401291/15384716

9：vs Code ：MySqlManageSystem.zip-MySQL Document resources -CSDN download



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Reunderstanding

EF Core  Database management
1. Create a database by instruction or update , Delete data table
EF Core Tool reference （ Package manager console ）- EF Core | Microsoft Docs