从WebApi中的Mysql数据库中检索数据到HttpRecquest？

Question

I am trying to retrieve a set of data from a MySQL database in a WebAPI application and access it through HTTP request from a mobile app. Hence I created a WebApi, a RestClient class and the class where I would show the data, this is my code.

Web API

[Produces("application/json")]
[Route("api/Blog")]
public class BlogController : Controller
{
    // GET: api/Blog
    [HttpGet]
    public  IEnumerable<string>  Get()
    {

    }

    // GET: api/Blog/5
    [HttpGet("{id}", Name = "GetBlogItems")]
    public string Get(int id)
    {

    }

    // POST: api/Blog
    [HttpPost]
    public void Post([FromBody]  RetrieveDataClass value)
    {
        string sqlstring = "server=; port= ; user id =;Password=;Database=;";
        MySqlConnection conn = new MySqlConnection(sqlstring);
        try
        {
            conn.Open();
        }
        catch (MySqlException ex)
        {
            throw ex;
        }
        string Query = "INSERT INTO test.blogtable (id,Telephone,CreatedSaved,Topic,Summary,Category,Body1,Body2,Body3,Body4)values('" + value.TopicSaved1 + "','" + Value.Telephone + "','" + Value.Created/Saved + "','" + value.TopicSaved1 + "','" +value.SummarySaved1 +"','" +value.CategoriesSaved1 +"','" +value.Body1 +"','" +value.Body2 +"','" +value.Body3 +"','" +value.Body4 +"');";
        MySqlCommand cmd = new MySqlCommand(Query, conn);
        cmd.ExecuteReader();
        conn.Close();

    }

    // PUT: api/Blog/5
    [HttpPut("{id}")]
    public void Put(int id, [FromBody]string value)
    {
    }

    // DELETE: api/ApiWithActions/5
    [HttpDelete("{id}")]
    public void Delete(int id)
    {
    }
}

So, in my database, I have three rows with a telephone number of +233892929292, after the filter I have to get three rows. and I would also filter to only the topic and summary column.

RestClient Class

   public class BlogRestClient<T>
{
    private const string WebServiceUrl = "http://localhost:57645/api/Blog/";

    public async Task<List<T>> GetAsync()
    {

        var httpClient = new HttpClient();

        var json = await httpClient.GetStringAsync(WebServiceUrl);

        var taskModels = JsonConvert.DeserializeObject<List<T>>(json);

        return taskModels;
    }


    public async Task<bool> PostAsync(T t)
    {

        var httpClient = new HttpClient();

        var json = JsonConvert.SerializeObject(t);

        HttpContent httpContent = new StringContent(json);

        httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");

        var result = await httpClient.PostAsync(WebServiceUrl, httpContent);

        return result.IsSuccessStatusCode;

    }

    public async Task<bool> PutAsync(int id, T t)
    {
        var httpClient = new HttpClient();

        var json = JsonConvert.SerializeObject(t);

        HttpContent httpContent = new StringContent(json);

        httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");

        var result = await httpClient.PutAsync(WebServiceUrl + id, httpContent);

        return result.IsSuccessStatusCode;
    }

    public async Task<bool> DeleteAsync(int id, T t)
    {
        var httpClient = new HttpClient();

        var response = await httpClient.DeleteAsync(WebServiceUrl + id);

        return response.IsSuccessStatusCode;
    }
}

ModelData Class

    public class ModelDataClass
    {
         public string Telephone ;
         public string Created/Saved ;
         public string TopicSaved1 ;
         public string SummarySaved1 ;
         public string CategoriesSaved1 ;
         public string Body1 ;
         public string Body2 ;
         public string Body3 ;
         public string Body4 ;


         public ModelDataClass()
         {

         }
    }

The Values for the strings in ModelDataClass are set in another class to post in MySQL database. Since that is not causing the problem in question, I have not included the code.

RetrieveDataClass

 public class RetrieveDataClass
    {
         public string Topic ;
         public string Summary ;

         public RetrieveDataClass()
         {
            GetDataEvent();
            AddBlog();
         }

          public void GetDataEvent()
         {
          BlogRestClient<ModelDataClass> restClient = new 
          BlogRestClient<ModelDataClass>();
            await restClient.GetAsync();
         }


      public ObservableCollection<ModelDataClass> BlogItems = new  
      ObservableCollection<ModelDataClass>();

    public void AddBlog()
    {
        BlogListView.ItemsSource = BlogItems;
    }
   }

Question1 How do I retrieve the data from, Mysql, to WebAPI accessed through the REST client class(It's for mobile so I have to use Http request)?

Question2 I would like to create a listView for each row I retrieve through the MySQL database. With the heading being the data in the topic column and the subheading is with the data in summary column.

Answer 1

Your application is designed with the Multitier Architecture pattern. As such, you need to ensure you have a separation of concerns.

The Web API will represent your presentation logic layer. It will parse the client's request, query for the data as required and format the returned data as needed.

The RetrieveClient can then handle the data access layer. It will manage access to the database, insert, update, delete as needed.

The key point here is to ensure that each layer talks to the other to perform actions and that you do not directly access the database in your presentation layer.

As such,

How to retrieve data?

In your Data Access Layer :

public class RetrieveDataClass
{
    private IDbConnection connection;

    public RetrieveDataClass(System.Data.IDbConnection connection)
    {
        // Setup class variables
        this.connection = connection;
    }

    /// <summary>
    /// <para>Retrieves the given record from the database</para>
    /// </summary>
    /// <param name="id">The identifier for the record to retrieve</param>
    /// <returns></returns>
    public EventDataModel GetDataEvent(int id)
    {
        EventDataModel data = new EventDataModel();

        string sql = "SELECT id,Telephone,CreatedSaved,Topic,Summary,Category,Body1,Body2,Body3,Body4 WHERE id = @id";
        using (IDbCommand cmd = connection.CreateCommand())
        {
            cmd.CommandText = sql;
            cmd.CommandType = CommandType.Text;

            IDbDataParameter identity = cmd.CreateParameter();
            identity.ParameterName = "@id";
            identity.Value = id;
            identity.DbType = DbType.Int32; // TODO: Change to the matching type for id column

            cmd.Parameters.Add(identity);

            try
            {
                connection.Open();
                using (IDataReader reader = cmd.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        data.id = reader.GetInt32(reader.GetOrdinal("id"));
                        // TODO : assign the rest of the properties to the object
                    }
                    else
                    {
                        // TODO : if method should return null when data is not found
                        data = null;
                    }
                }
                // TODO : Catch db exceptions
            } finally
            {
                // Ensure connection is always closed
                if (connection.State != ConnectionState.Closed) connection.Close();
            }
        }

        // TODO : Decide if you should return null, or empty object if target cannot be found.
        return data;
    }

    // TODO : Insert, Update, Delete methods
}

The above will get a record from the database, and return it as an object. You can use ORM libraries such as EntityFramework or NHibernate instead but they have their own learning curve.

How to return the data?

Your client will call the WebAPI, which in turn query for the data from the data access layer.

[Produces("application/json")]
[Route("api/Blog")]
public class BlogController : Controller
{
    // TODO : Move the connection string to configuration
    string sqlstring = "server=; port= ; user id =;Password=;Database=;";

    // GET: api/Blog
    /// <summary>
    /// <para>Retrieves the given record from the database</para>
    /// </summary>
    /// <param name="id">Identifier for the required record</param>
    /// <returns>JSON object with the data for the requested object</returns>
    [HttpGet]
    public IEnumerable<string> Get(int id)
    {
        IDbConnection dbConnection = System.Data.Common.DbProviderFactories.GetFactory("MySql.Data.MySqlClient");
        RetrieveDataClass dal = new RetrieveDataClass(dbConnection);

        EventDataModel data = dal.GetDataEvent(id);
        if (data != null)
        {
            // Using Newtonsoft library to convert the object to JSON data
            string output = Newtonsoft.Json.JsonConvert.SerializeObject(data);

            // TODO : Not sure if you need IEnumerable<string> as return type
            return new List<string>() { output };
        } else
        {
            // TODO : handle a record not found - usually raises a 404
        }
    }

    // TODO : other methods
}

There are lots of other examples online on how to access the data via API. Have a look on google and review. A few that come to mind are

https://docs.microsoft.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-2.2&tabs=visual-studio

https://docs.microsoft.com/en-us/aspnet/web-api/overview/getting-started-with-aspnet-web-api/tutorial-your-first-web-api

Answer 2

i solved the problem.

WebApi

[Produces("application/json")]
[Route("api/Blog")]
public class BlogController : Controller
{
// GET: api/Blog
[HttpGet]
 public List<BlogViews>  Get()
    {

            string sqlstring = "server=; port= ; user id =;Password=;Database=;";
            MySqlConnection conn = new MySqlConnection(sqlstring);
            try
            {
                conn.Open();
            }
            catch (MySqlException ex)
            {
                throw ex;
            }
            string Query = "SELECT * FROM test.blogtable where `Telephone` ='Created'";
            MySqlCommand cmd = new MySqlCommand(Query, conn);
            MySqlDataReader MSQLRD = cmd.ExecuteReader();
            List<BlogViews> GetBlogList = new List<BlogViews>();

            if (MSQLRD.HasRows)
            {

              while (MSQLRD.Read())
              {
                BlogViews BV = new BlogViews();
                BV.id = (MSQLRD["id"].ToString());
                BV.DisplayTopic = (MSQLRD["Topic"].ToString());
                BV.DisplayMain = (MSQLRD["Summary"].ToString());
                GetBlogList.Add(BV);
              }
            }
            conn.Close();
        return GetBlogList;
    }

// GET: api/Blog/5
[HttpGet("{id}", Name = "GetBlogItems")]
public string Get(int id)
{

}

// POST: api/Blog
[HttpPost]
public void Post([FromBody]  RetrieveDataClass value)
{
    string sqlstring = "server=; port= ; user id =;Password=;Database=;";
    MySqlConnection conn = new MySqlConnection(sqlstring);
    try
    {
        conn.Open();
    }
    catch (MySqlException ex)
    {
        throw ex;
    }
    string Query = "INSERT INTO test.blogtable (id,Telephone,CreatedSaved,Topic,Summary,Category,Body1,Body2,Body3,Body4)values('" + value.TopicSaved1 + "','" + Value.Telephone + "','" + Value.Created/Saved + "','" + value.TopicSaved1 + "','" +value.SummarySaved1 +"','" +value.CategoriesSaved1 +"','" +value.Body1 +"','" +value.Body2 +"','" +value.Body3 +"','" +value.Body4 +"');";
    MySqlCommand cmd = new MySqlCommand(Query, conn);
    cmd.ExecuteReader();
    conn.Close();

}

// PUT: api/Blog/5
[HttpPut("{id}")]
public void Put(int id, [FromBody]string value)
{
}

// DELETE: api/ApiWithActions/5
[HttpDelete("{id}")]
public void Delete(int id)
{
}

}

RetriveDataClass

   public class RetrieveDataClass
   {

     public RetrieveDataClass()
     {
       AddBlog();
     }
  public class BlogViews
    {
        public string id { get; set; }
        public string DisplayTopic { get; set; }
        public string DisplayMain { get; set; }
        public ImageSource BlogImageSource { get; set; }
    }

    public List<BlogViews> BlogList1 = new List<BlogViews>();
    public async Task< List<BlogViews>> GetBlogs()
    {
        BlogRestClient<BlogViews> restClient = new BlogRestClient<BlogViews>();
        var BlogV = await restClient.GetAsync();
        return BlogV;
    }

    public async void AddBlog()
    {
        BlogList1 = await GetBlogs();
        BlogListView.ItemsSource = BlogList1;
    }


}

so now i get a listview ,which contains each row from the database and each item in the listview heading is DisplayTopic and subheading is DisplayMain.