Develop Reference

How can I add new row to database with values stored in ObservableCollection?

So I have two ObservableCollections:
ObservableCollection<Student> studentslist
ObservableCollection<Subject> subjectslist
and I'm passing them to class where I have set up whole communication with sql database.
studentslist contains values passed by:
StudentsList.Add(new Student { IdStudent = newStudentId, Name = NameBox.Text, Surname = SurnameBox.Text, Index = IndexBox.Text })
subjectlist contains values from checked checkboxes in my listbox (I'm still not sure if this is correct):
var selectedSubjects = SubjectList.Where(subjects => subjects.IsChecked == true);
var selectedSubjectsCollection = new ObservableCollection<Subject>(selectedSubjects);
and this is my Subject class:
public class Subject
{
public int IdSubject{ get; set; }
public string subject{ get; set; }
public bool IsChecked { get; set; }
public override string ToString()
{
return $"{subject}";
}
}
Now in my class, responsible for connection with sql data base, I've created method which grabs both of this collections and based on their values I would like to create new record in database:
public void addRecord(ObservableCollection<Student> studentslist, ObservableCollection<Przedmiot> subjectslist)
{
OpenConection();
//...
CloseConnection();
}
In database I have Student table:
Student(IdStudent, FirstName, LastName, IndexNumber)
and Subject table:
Subject(IdSubject, Name)
And as far as I can read data from my data base, I don't know how in correct way pass these values to corresponding values in data base.

I like to do this kind of thing using stored procedures to minimise the amount of T-SQL code in the app.
An example would be:
public static void InsertSubject(Przedmiot subject)
{
using (SqlConnection conn = new SqlConnection("Connection String"))
{
try
{
SqlCommand command = new SqlCommand("dbo.InsertSubject", conn) { CommandType = CommandType.StoredProcedure };
command.Parameters.Add(new SqlParameter("#IdSubject", subject.IdSubject));
command.Parameters.Add(new SqlParameter("#Name", subject.subject));
conn.Open();
command.ExecuteNonQuery();
}
catch (Exception ex)
{
// handle exceptions
}
}
}
You would then have a stored procedure with the same signature to perform the INSERT, i.e.:
CREATE PROCEDURE dbo.InsertSubject
#IdSubject int
, #Name varchar(50)
AS
...
GO
If you want to pass in the entire collection you could implement a foreach loop in the above example.
Personally I like to call these methods once per insert and have it as an int returning method (for example) so I can pass some data out, e.g., the ID of the inserted row.

How to update data from child class variables using parent class function?

i'm trying to practise my c# by doing a little exercise creating a basic ORM.
So i have 3 files, my Main program calling my Model:
public Form1()
{
InitializeComponent();
Pessoa mPessoa = new Pessoa();
mPessoa.First();
MessageBox.Show(mPessoa.nome);
}
My child model class:
class Pessoa:Model
{
public int id;
public string nome;
public string telefone;
public Pessoa()
{
Table = "Pessoa";
Conn = "Principal";
}
}
And my parent Model Class:
class Model:Conn
{
protected string Table;
protected string Conn;
public void First()
{
OpenConnection();
string query = "SELECT * from " + Table + " Where id = 1 limit 1";
DataTable oDT = new DataTable();
MySqlDataAdapter da = new MySqlDataAdapter(query, connection);
da.Fill(oDT);
foreach (var column in oDT.Columns)
{
}
}
The question is: How can i update the child class variables (id, nome and telefone) based on the results from my parent class funcion?
As you can see, i've tried to use dynamic variable names using that foreach with the columns from the result, but i'm stuck because i dont know how to properly set the values.

C# - MySql - Best way to convert data from MySqlDataReader to different models

I have experience in working and fixing bugs with existing code bases that implement MySql code, but have to design a new program from scratch at my new job. I am not sure what is the best way to return data from MySqlDataReader to my custom models. Please advise!
Here's what I have,
Folder structure:
Models (folder)
Metadata.cs
User.cs
MySqlDb.cs
Metadata.cs: Reresents data from metadata table
public class Metadata
{
public int Id { get; set; }
public string Title { get; set; }
public string Sku { get; set; }
public bool IsLive { get; set; }
}
User.cs: Represents data from user table
public class User
{
public int Id { get; set; }
public string UserName { get; set; }
public int Age { get; set; }
public string Address { get; set; }
}
MySqlDb.cs
using MySql.Data;
using MySql.Data.MySqlClient;
public class MySqlDb
{
public MySqlConnection Connection { get; set;}
public MySqlDb(string connectionString)
{
Connection = new MySqlConnection(connectionString);
}
public List<Metadata> RunSelectQueryForMetadata(string query)
{
var rdr = new MySqlCommand(query, Connection).ExecuteReader();
var metadata = new List<Metadata>();
using (rdr)
{
while(rdr.Read())
{
metadata.Add(
new Metadata {
Id = rdr["id"],
Title = rdr["title"],
Sku = rdr["sku"],
IsLive = rdr["islive"],
});
} // while
} // using
return metadata;
} // public void RunSelectQuery(string query)
} // public class MySqlDb
If I try to get Users data, I am thinking of writing another method (RunSelectQueryForUsers). I would like to avoid writing different methods for different tables. I am not sure how to use one method for retrieving data from different tables with different data structures and typecast them to the Model I want.
Any help is greatly appreciated!!

One way is to use micro-orm such as Dapper which is a simple object mapper built for .Net. Dapper extends the IDbConnection by providing useful extension methods to query your database.
Example of implementing dapper within your current menthod:
public List<Metadata> RunSelectQueryForMetadata(string query)
{
var metadata = new List<Metadata>();
try // implement proper error handling
{
Connection.Open();
metadata = Connection.Query<Metadata>(query).ToList();
Connection.Close();
}
catch(Exception ex)
{
// error here
}
return metadata;
}
Some useful links:
Dapper Github
Dapper Tutorial
Converting it to generic method: (not tested right now)
public List<T> RunSelectQuery<T>(string query)
{
try // implement proper error handling
{
Connection.Open();
metadata = Connection.Query<T>(query).ToList();
Connection.Close();
}
catch(Exception ex)
{
// error here
}
return metadata;
}
and use something like this below:
List<Metadata> myMetadata = RunSelectQuery<Metadata>(query);

I prefer a pattern more like this:
public class MySqlDb
{
//1. This should not be public!
// Keeping it private forces other code to go through your public methods,
// rather than using the connection directly.
// Even better if the class knows how to read the string from a
// config rile rather than accepting it via the constructor.
//2. Don't save a connection object for re-use.
// ADO.Net has a connection pooling feature that works when you
// create new objects for most queries
private string ConnectionString { get; set;}
public MySqlDb(string connectionString)
{
ConnectionString = connectionString;
}
//1. Use IEnumerable instead of List
// ...don't pull all of the results into memory at the same time until/unless you really have to.
//2. Methods that accept query strings should also accept parameters.
// Otherwise you are forced to build sql strings in insecure crazy-vulnerable ways
public IEnumerable<Metadata> RunSelectQueryForMetadata(string query, IEnumerable<MySqlParameter> parameters)
{
using (var cn = new MySqlConnection(ConnectionString))
using (var cmd = new MySqlCommand(query, cn))
{
if (parameters != null)
{
cmd.Parameters.AddRange(parameters.ToArray());
}
cn.Open();
using(var rdr = cmd.ExecuteReader())
{
while(rdr.Read())
{
yield return new Metadata {
Id = rdr["id"],
Title = rdr["title"],
Sku = rdr["sku"],
IsLive = rdr["islive"],
};
}
rdr.Close();
}
}
}
}
Ultimately, the ideal is for the RunSelectQuery__() method to be generic and private, and for public methods to not accept SQL statements. The goal is to force all SQL in your program to live in the MySqlDb class. Each query has a method that accepts specific typed inputs, and returns typed output. The reason you have that goal is to make it easy to manage your database access and easy to audit that all of your SQL code is safely using parameters (and not vulnerable to sql injection attacks! ). You want something like this:
//updated to remove the earlier explanatory comments
// and show example methods for isolating SQL from the rest of the application.
public class MySqlDb
{
private string ConnectionString { get; set;}
private string ReadConnectionStringFromConfigFile()
{
//TODO
throw NotImplementedException();
}
public MySqlDb()
{
ConnectionString = ReadConnectionStringFromConfigFile();
}
//This is now PRIVATE and generic, and allows for parameterized queries
private IEnumerable<T> RunSelectQuery(string query, Func<IDataReader, T> translateRecord, IEnumerable<MySqlParameter> parameters)
{
using (var cn = new MySqlConnection(ConnectionString))
using (var cmd = new MySqlCommand(query, cn))
{
if (parameters != null)
{
cmd.Parameters.AddRange(parameters.ToArray());
}
cn.Open();
using(var rdr = cmd.ExecuteReader())
{
while(rdr.Read())
{
yield return translateRecord(rdr);
}
rdr.Close();
}
}
}
////// Example methods showing how to use the generic method above
// These methods are the only public part of your class
public MetaData GetMetaDataById(int ID)
{
string sql = "SELECT * FROM MetatData WHERE ID= #ID";
var parameters = new List<MySqlParameters> {
new MySqlParameter() {
ParameterName = "#ID",
MySqlDbType = MySqlDbType.Int32,
Value = ID
}
};
return RunSelectQuery<MetaData>(sql, parameters, r =>
new Metadata {
Id = r["id"],
Title = r["title"],
Sku = r["sku"],
IsLive = r["islive"],
}).FirstOrDefault();
}
public IEnumerable<MetaData> GetAllMetaData()
{
string sql = "SELECT * FROM MetatData";
return RunSelectQuery<MetaData>(sql, null, r =>
new Metadata {
Id = r["id"],
Title = r["title"],
Sku = r["sku"],
IsLive = r["islive"],
});
}
public User GetUserByID(int ID)
{
string sql = "SELECT * FROM User WHERE ID= #ID";
var parameters = new List<MySqlParameters> {
new MySqlParameter() {
ParameterName = "#ID",
MySqlDbType = MySqlDbType.Int32,
Value = ID
}
};
return RunSelectQuery<User>(sql, parameters, r =>
new Metadata {
Id = r["id"],
UserName = r["UserName"],
Age = r["Age"],
Address = r["Address"],
}).FirstOrDefault();
}
public User GetUserByUsername(string UserName)
{
string sql = "SELECT * FROM User WHERE Username= #UserName";
var parameters = new List<MySqlParameters> {
new MySqlParameter() {
ParameterName = "#UserName",
MySqlDbType = MySqlDbType.VarChar,
Size = 20, //guessing at username lenght
Value = UserName
}
};
return RunSelectQuery<User>(sql, parameters, r =>
new Metadata {
Id = r["id"],
UserName = r["UserName"],
Age = r["Age"],
Address = r["Address"],
}).FirstOrDefault();
}
public IEnumerable<User> FindUsersByAge(int Age)
{
string sql = "SELECT * FROM User WHERE Age = #Age";
var parameters = new List<MySqlParameters> {
new MySqlParameter() {
ParameterName = "#Age",
MySqlDbType = MySqlDbType.Int32,
Value = Age
}
};
return RunSelectQuery<User>(sql, parameters, r =>
new Metadata {
Id = r["id"],
UserName = r["UserName"],
Age = r["Age"],
Address = r["Address"],
});
}
}
In larger applications, you abstract this further into a separate project, with a private class for the lower-level methods that are private here, and a public class for each of the object types you use via that database. You might even go full-blown service-oriented architecture, where you get all your data via web service calls, and only the service layer talks directly to any database.
Of course, at this level you can also use a mirco-ORM like Dapper. Micro-ORMs will help you avoid re-writing the same mapping code over and over, and also help more with the INSERT/UPDATE side of data operations. Their goal is to take over as much of the boilerplate code for you as they can.
The advantage of a micro-ORM over a full ORM is it keeps you closer to the SQL. This is a good thing. Full-blown ORMs like Entity Framework or NHibernate effectively force you to learn a whole new language on top of the SQL, while mostly limiting you to basic SQL statements that often lose the advantages from the "relational" part of a relational database. Eventually, you often end up needing to understand and write complex raw SQL anyway to optimize performace. Micro-ORMs try to offer a happy-medium... taking away as much of the boiler plate code needed to talk to a database as they can, while still leaving you to write your own SQL.

While not tailored to using MySql and straight up sql, the below code snippets provide a means to do what you're asking using generics. Could use some improvements though...
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Data.General
{
public abstract class DataObject
{
protected abstract void Initialize(IDataRecord dataRow);
private static string _connectionString = "";
/// <summary>
/// Loads a single data object from the results of a stored procedure.
/// </summary>
protected static T ReadObject<T>(string procedureName, SqlParameter[] sqlParameters, Type dataType)
{
DataObject returnItem = null;
using (SqlConnection sqlConnection = new SqlConnection(GetConnectionString()))
using (SqlCommand command = BuildCommand(sqlConnection, procedureName, sqlParameters))
{
sqlConnection.Open();
//Execute the reader for the given stored proc and sql parameters
using (IDataReader reader = command.ExecuteReader())
{
//If we get no records back we'll still return null
while (reader.Read())
{
returnItem = (DataObject)Activator.CreateInstance(typeof(T));
returnItem.Initialize(reader);
break;
}
}
}
//Return our DataObject
return (T)Convert.ChangeType(returnItem, dataType);
}
/// <summary>
/// Reads a collection of data objects from a stored procedure.
/// </summary>
protected static List<T> ReadObjects<T>(string procedureName, SqlParameter[] sqlParameters)
{
//Get cached data if it exists
List<T> returnItems = new List<T>();
T dataObject;
using (SqlConnection sqlConnection = new SqlConnection(GetConnectionString()))
using (SqlCommand command = BuildCommand(sqlConnection, procedureName, sqlParameters, null))
{
sqlConnection.Open();
//Execute the reader for the given stored proc and sql parameters
using (IDataReader reader = command.ExecuteReader())
{
//If we get no records back we'll still return null
while (reader.Read())
{
dataObject = (T)Activator.CreateInstance(typeof(T));
(dataObject as DataObject).Initialize(reader);
returnItems.Add(dataObject);
}
}
}
//Return the DataObjects
return returnItems;
}
/// <summary>
/// Builds a SQL Command object that can be used to execute the given stored procedure.
/// </summary>
private static SqlCommand BuildCommand(SqlConnection sqlConnection, string procedureName, SqlParameter[] sqlParameters, SqlTransaction sqlTransaction = null)
{
SqlParameter param;
SqlCommand cmd = new SqlCommand(procedureName, sqlConnection);
if (sqlTransaction != null)
{
cmd.Transaction = sqlTransaction;
}
cmd.CommandType = CommandType.StoredProcedure;
// Add SQL Parameters (if any)
foreach (SqlParameter parameter in sqlParameters)
{
param = new SqlParameter(parameter.ParameterName, parameter.DbType);
param.Value = parameter.Value;
cmd.Parameters.Add(param);
}
return cmd;
}
private static string GetConnectionString()
{
return _connectionString;
}
public static void SetConnectionString(string connectionString)
{
_connectionString = connectionString;
}
}
}
namespace Data.Library
{
public class Metadata : General.DataObject
{
protected Data.Model.Metadata _metaData;
public Data.Model.Metadata BaseModel
{
get { return _metaData; }
set { _metaData = value; }
}
//Typically I have properties in here pointing to the Data.Model class
protected override void Initialize(System.Data.IDataRecord dataRow)
{
_metaData = new Model.Metadata();
_metaData.Id = Convert.ToInt32(dataRow["Id"].ToString());
_metaData.Title = (dataRow["Title"].ToString());
_metaData.Sku = (dataRow["Sku"].ToString());
_metaData.IsLive = Convert.ToBoolean(dataRow["IsLive"].ToString());
}
public static Metadata ReadByID(int id)
{
return General.DataObject.ReadObject<Metadata>("dbo.s_MetadataGet", new[] { new SqlParameter("#ID", id) },
typeof(Metadata));
}
public static Metadata[] ReadBySku(string sku)
{
List<Metadata> metaDatas = General.DataObject.ReadObjects<Metadata>("dbo.s_MetadataGetBySku", new[] { new SqlParameter("#Sku", sku) });
return metaDatas.ToArray();
}
}
}
namespace Data.Model
{
public class Metadata
{
public int Id { get; set; }
public string Title { get; set; }
public string Sku { get; set; }
public bool IsLive { get; set; }
}
}

Insert a list using dapper.NET C#

I'd like to insert a list of objects in an SQL table.
I know this question here but I don't understand.
Here is my class :
public class MyObject
{
public int? ID { get; set; }
public string ObjectType { get; set; }
public string Content { get; set; }
public string PreviewContent { get; set; }
public static void SaveList(List<MyObject> lst)
{
using (DBConnection connection = new DBConnection())
{
if (connection.Connection.State != ConnectionState.Open)
connection.Connection.Open();
connection.Connection.Execute("INSERT INTO [MyObject] VALUE()",lst);
}
}
}
I'd like to know how could I insert my list using Dapper, I don't want to iterate on the list and save them one by one, I would like to insert all of them in one request.

You can insert these just as you would INSERT a single line:
public class MyObject
{
public int? ID { get; set; }
public string ObjectType { get; set; }
public string Content { get; set; }
public string PreviewContent { get; set; }
public static void SaveList(List<MyObject> lst)
{
using (DBConnection connection = new DBConnection())
{
if (connection.Connection.State != ConnectionState.Open)
connection.Connection.Open();
connection.Connection.Execute("INSERT INTO [MyObject] (Id, ObjectType, Content, PreviewContent) VALUES(#Id, #ObjectType, #Content, #PreviewContent)", lst);
}
}
}
Dapper will look for class members named after your SQL parameters (#Id, #ObjectType, #Content, #PreviewContent) and bind them accordingly.

You need pass a table-value parameter.
1. Create table type in your sql database.
2. Create DynamicParameters and add the datatable (new values) to it.
3. Execute.
SQL:
CREATE TYPE [dbo].[tvMyObjects] AS TABLE(
[ID] INT,
[ObjectType] [varchar](70), /*Length on your table*/
[Content] [varchar](70), /*Length on your table*/
[PreviewContent] [varchar](70) /*Length on your table*/
)
C#:
var dynamicParameters = new DynamicParameters();
dynamicParameters.Add("#MyObjects", lst
.AsTableValuedParameter("dbo.tvMyObjects", new[]
{
"ID" ,
"ObjectType",
"Content",
"PreviewContent"
}));
connection.Connection.Execute(#"
INSERT INTO [MyObject] (Id, ObjectType, Content, PreviewContent)
SELECT Id,
ObjectType,
Content,
PreviewContent
FROM #MyObjects", dynamicParameters);
More info: https://www.codeproject.com/Articles/835519/Passing-Table-Valued-Parameters-with-Dapper

You would just change your SQL to a valid insert statment that has parameters matching the names of the properties on your class.
INSERT INTO MyObject VALUES(#Id, #ObjectType, #Content, #PreviewContent)
Or if you need to specify the table columns (where these aren't all the columns in the table, for example):
INSERT INTO MyObject (Id, ObjectType, Content, PreviewContent)
VALUES(#Id, #ObjectType, #Content, #PreviewContent)

You can use the Dapper.Contrib extensions to simplify the code. I've found this works well for a few hundred records, but for very large inserts, I switch to SqlBulkCopy. The synchronous version is Insert instead of InsertAsync (as you'd guess). Make sure your entities are named as Dapper expects and have a primary key, Id, or, add annotations for table name and key to your entity.
using using Dapper.Contrib.Extensions; //Git
public async Task SaveChangesAsync(IList<MyEntity> myEntityValues)
{
var conn = new SqlConnection(myconnectionString);
if(conn.State != ConnectionState.Open)
conn.Open();
await conn.InsertAsync(myEntityValues);
if (conn.State != ConnectionState.Closed)
{
conn.Close();
conn.Dispose();
}
}

In case you need new naming or combined sources:
await connection.ExecuteAsyncWithRetry(SqlSave,
list.Select(x =>
new
{
x.ID,
SomeNew = NewSource.SomeNew, // From other source
NameNew = x.NameOld, // New naming
x.ObjectType,
x.Content,
x.ContentList = String.Join(",", x.Content) // Data transform
}));

In Entity Framework database-first approach how to return multiple result sets from a stored procedure?

I am working with Entity Framework using the database-first approach. I created a stored procedure in MySQL that returns multiple sets, I want to get all result sets on a single hit not only the top one result set.
In my stored procedure I am passing arguments too.

You can use SQLQuery to execute your procedure:
public partial class NorthwindContext
{
public IEnumerable<CustomerOrderHistory> CustomerOrderHistory(string customerID)
{
var customerIDParameter = customerID != null ?
new SqlParameter("#CustomerID", customerID) :
new SqlParameter("#CustomerID", typeof(string));
return Database.SqlQuery<CustomerOrderHistory>("CustOrderHist #CustomerID", customerIDParameter);
}
}
and the model looks like:
public partial class CustomerOrderHistory
{
public string ProductName { get; set; }
public Nullable<int> Total { get; set; }
}
It's sample based on Northwind Database

use basic reader and make use of reader.NextResult method.
var cmd = db.Database.Connection.CreateCommand();
cmd.CommandText = "some command here";
try
{
db.Database.Connection.Open();
var reader = cmd.ExecuteReader();
var books = ((IObjectContextAdapter)db)
.ObjectContext
.Translate<Book>(reader, "Books", MergeOption.AppendOnly);
// Move to second result set and read authors
reader.NextResult();
var authors = ((IObjectContextAdapter)db)
.ObjectContext
.Translate<Author>(reader, "Authors", MergeOption.AppendOnly);
}
finally
{
db.Database.Connection.Close();
}