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ASP.NET Core Entity Framework call stored procedure

I am using ASP.NET Core Entity Framework and I would like to call a simple stored procedure.
I created the stored procedure in my migrations like this:
public partial class spGetAvailableCourses : Migration
{
protected override void Up(MigrationBuilder migrationBuilder)
{
var sp = #"CREATE PROCEDURE [dbo].[GetAvailableCourses]
AS
BEGIN
SELECT COUNT(courses.Enrolled) FROM Courses WHERE Courses.Capacity > Courses.Enrolled;
END";
migrationBuilder.Sql(sp);
}
I can call the stored procedure in SQL Server with the following command.
EXEC dbo.GetAvailableCourses
But when I try and call the stored procedure in in my ICourseRepository, it doesn't work, I get minus one returned.
Can someone please tell me the correct of calling the stored procedure? Thanks
public class CourseRepository : ICourseRepository
{
private readonly DataContext _context;
public CourseRepository(DataContext context)
{
_context = context;
}
public Task<CoursesAvailableCount> CoursesAvailableCount()
{
var ss = _context.Database.ExecuteSqlRaw("GetAvailableCourses");
return null;
}
I also tried
public async Task<CoursesAvailableCount> CoursesAvailableCount()
{
var s = await _context.Database.ExecuteSqlCommandAsync("GetAvailableCourses");
}

In addition to the ExecuteSqlCommand method, the DbContext.Database property provides an API that allows you to perform ADO.NET operations directly. The GetDbConnection method returns a DbConnection object representing the context's underlying connection. From that point, you can revert to the familiar ADO.NET APIs:
using (var command = _context.Database.GetDbConnection ().CreateCommand ())
{
command.CommandText = "SP_NAME";
command.CommandType = CommandType.StoredProcedure;
_context.Database.OpenConnection ();
using (var result = command.ExecuteReader ())
{
if (result.HasRows)
{
result.Read ();
var x = result.GetInt32 (0); // x = your sp count value
}
}
}
EDIT (extension example):
public static class EfCoreExtensions
{
public static int? Execute_SingleValue_SP_AsInt(this AppDbContext context,string SpName)
{
using (var command = context.Database.GetDbConnection().CreateCommand())
{
command.CommandText = SpName;
command.CommandType = System.Data.CommandType.StoredProcedure;
context.Database.OpenConnection();
using (var result = command.ExecuteReader())
{
if (result.HasRows)
{
result.Read();
var x = result.GetInt32(0); // x = your sp count value
return x;
}
return null;
}
}
}
}

For .net core 3.1, using stored procedures with parameters. Use the below code. It works for me. Enjoy!!!
using (var command = DbContext.Database.GetDbConnection().CreateCommand())
{
command.CommandText = "Users_SP";
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add(new SqlParameter(“#usernme”, username));
command.Parameters.Add(new SqlParameter("#TransDate", DateTime.Now));
DbContext.Database.OpenConnection();
using (var result = command.ExecuteReader())
{
if (result.HasRows)
{
while (result.Read())
{
response = Convert.ToString(result["Amount"]);
}
}
}
}

From child class, call base class method while using child fields

I have created a small ETL program with a single method that only takes a connection string for the source database and a connection string for a target database.
Basically, it has 5 steps:
Step 1. Select data from the source.
Step 2. Create a temporary table on the target.
Step 3. Load data from the source into the temporary on the target.
Step 4. Merge the data from temporary table into the actual target table.
Step 5. Drop the temporary table
This works great for a single transformation that needs to take place, but I have about 20 different ETL "jobs" that need to take place.
So instead of copying and pasting the same method verbatim 19 different times, I would like to define a base class that defines this single method one time, and then call this single method from each child class, with its own select, create, merge and drop statements.
Is this possible?
Base Class:
public class ETLBase
{
private static string Select;
private static string CreateTemp;
private static string Merge;
private static string CleanUp;
private static string DestinationTable;
public static void ExecuteJob(string sourceConnectionString, string destinationConnectionString)
{
using (OracleConnection sourceConnection = new OracleConnection(sourceConnectionString))
{
sourceConnection.Open();
OracleCommand selectCommand = new OracleCommand(Select, sourceConnection);
OracleDataReader reader = selectCommand.ExecuteReader();
using (SqlConnection destinationConnection = new SqlConnection(destinationConnectionString))
{
destinationConnection.Open();
SqlCommand createTempCommand = new SqlCommand(CreateTemp, destinationConnection);
createTempCommand.ExecuteNonQuery();
SqlCommand mergeCommand = new SqlCommand(Merge, destinationConnection);
SqlCommand dropCommand = new SqlCommand(CleanUp, destinationConnection);
using (SqlBulkCopy bulkCopy = new SqlBulkCopy(destinationConnection))
{
bulkCopy.DestinationTableName = DestinationTable;
try
{
bulkCopy.WriteToServer(reader);
mergeCommand.ExecuteNonQuery();
dropCommand.ExecuteNonQuery();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
reader.Close();
}
}
}
}
}
}
Child Class:
public class ChildETL: ETLBase
{
private static string Select = #"Select THIS DataStatement";
private static string CreateTemp = #"CREATE TABLE Statement";
private static string Merge = #"Merge Table statement";
private static string CleanUp = "DROP TABLE Statement";
private static string DestinationTable = "##TempTable";
}
And then execute it something like this, but where each child class uses its own defined fields, so it uses it's own SQL statements.
public class Program
{
public static void Main(string[] args)
{
IConfiguration config = new ConfigurationBuilder()
.AddJsonFile("appsettings.json", true, true)
.Build();
string schoolDBConnection = config["SchoolConnection"];
string courseDBConnection = config["CourseConnection"];
string teacherDBConnection = config["Connection"];
ChildETLA.ExecuteJob(schoolDBConnection, courseDBConnection);
ChildETLB.ExecuteJob(teacherDBConnection, courseDBConnection);
//...and so on for each child ETL class
}
}

First of all, you need to run "ExecuteJob()" polymorphically, which means behaviour of "ExeceuteJob" will be different based on source and destination connection string. You can't achieve polymorphism for static function or properties. First of all, you need to refactor it to instance method by taking out the "Static" keywords. Also, the behaviour of the base class is deciding by child classes so that nobody should be able to create an object of base class to make it an abstract class. Look at your code you have two behaviours one for school and another one for the teacher. So you have to create two different child classes which inherit the abstract base class. It is the responsibility of object creation to compose object with source and destination connection string so pass it to the constructor and set it while creating the object itself. Please find the refactored code,
public abstract class ETLBase
{
private readonly string sourceConnectionString;
private readonly string destinationConnectionString;
protected virtual string Select { get; set; } = #"Select THIS DataStatement";
protected virtual string CreateTemp { get; set; } = #"CREATE TABLE Statement";
protected virtual string Merge { get; set; } = #"Merge Table statement";
protected virtual string CleanUp { get; set; } = "DROP TABLE Statement";
protected virtual string DestinationTable { get; set; } = "##TempTable";
protected ETLBase(string sourceConnectionString, string destinationConnectionString)
{
this.sourceConnectionString = sourceConnectionString;
this.destinationConnectionString = destinationConnectionString;
}
public void ExecuteJob()
{
using (OracleConnection sourceConnection = new OracleConnection(sourceConnectionString))
{
sourceConnection.Open();
OracleCommand selectCommand = new OracleCommand(Select, sourceConnection);
OracleDataReader reader = selectCommand.ExecuteReader();
using (SqlConnection destinationConnection = new SqlConnection(destinationConnectionString))
{
destinationConnection.Open();
SqlCommand createTempCommand = new SqlCommand(CreateTemp, destinationConnection);
createTempCommand.ExecuteNonQuery();
SqlCommand mergeCommand = new SqlCommand(Merge, destinationConnection);
SqlCommand dropCommand = new SqlCommand(CleanUp, destinationConnection);
using (SqlBulkCopy bulkCopy = new SqlBulkCopy(destinationConnection))
{
bulkCopy.DestinationTableName = DestinationTable;
try
{
bulkCopy.WriteToServer(reader);
mergeCommand.ExecuteNonQuery();
dropCommand.ExecuteNonQuery();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
reader.Close();
}
}
}
}
}
And the child classes,
public class ChildETLSchool : ETLBase
{
public ChildETLSchool(string sourceConnectionString, string destinationConnectionString)
: base(sourceConnectionString, destinationConnectionString)
{
//Change values of below lines only if you want to override the values
//Select = #"Select THIS DataStatement";
//CreateTemp = #"CREATE TABLE Statement";
//Merge = #"Merge Table statement";
//CleanUp = "DROP TABLE Statement";
//DestinationTable = "##TempTable";
}
}
public class ChildETLTeacher : ETLBase
{
public ChildETLTeacher(string sourceConnectionString, string destinationConnectionString)
: base(sourceConnectionString, destinationConnectionString)
{
//Change values of below lines only if you want to override the values
//Select = #"Select THIS DataStatement";
//CreateTemp = #"CREATE TABLE Statement";
//Merge = #"Merge Table statement";
//CleanUp = "DROP TABLE Statement";
//DestinationTable = "##TempTable";
}
}
And the object creation in main function,
static void Main(string[] args)
{
IConfiguration config = new ConfigurationBuilder()
.AddJsonFile("appsettings.json", true, true)
.Build();
string schoolDBConnection = config["SchoolConnection"];
string courseDBConnection = config["CourseConnection"];
string teacherDBConnection = config["Connection"];
var childETLSchool = new ChildETLSchool(schoolDBConnection, courseDBConnection);
var childETLTeacher = new ChildETLTeacher(teacherDBConnection, courseDBConnection);
childETLSchool.ExecuteJob();
childETLTeacher.ExecuteJob();
}

How to manually (via code) apply DbMigration which was manually crafted?

I manually created a class
public class AddClientsTable : DbMigration, IMigrationMetadata
{
string IMigrationMetadata.Id
{
get { return "201611281757258_AddClientsTable"; }
}
string IMigrationMetadata.Source
{
get { return null; }
}
string IMigrationMetadata.Target
{
get { return "AddClientsTable-Migration"; }
}
public override void Up() {
CreateTable("Clients", t => new {
ClientId = t.Guid(name:"ClientId"),
Name = t.String()
})
.PrimaryKey( t => t.ClientId, "ClientId")
.Index( t => t.ClientId, "PK_Clients", true);
}
public override void Down() {
DropIndex("Clients", "PK_Clients");
DropTable("Clients");
}
}
and i want to apply it via code-first migrations from code like this :
var migration = new AddClientsTable();
migration.Up();
context.RunMigration(migration);
which I stole from here but when I run the code I'm getting this exception :
Unable to cast object of type 'System.Data.Entity.Migrations.Model.CreateIndexOperation' to type 'System.Data.Entity.Migrations.Model.HistoryOperation'.
HistoryOperation is the operation which updates __MigrationHistory table ? so How do I do that via code ?
Am I missing something or the EntityFrameowrk Update-Database command does more than what I'm aware of ?

It doesn't make sense to cherry pick a migration and run it, because the migrations are cumulative and must be run in sequence. As such, you'd be better to run the equivalent of update-database powershell command at application startup.
Here's some code we use to do that:
In the Configuration.cs class constructor (this file was made when you enable-migrations)
AutomaticMigrationsEnabled = false;
AutomaticMigrationDataLossAllowed = false;
then at app startup call the following method:
public static void ApplyDatabaseMigrations()
{
//Configuration is the class created by Enable-Migrations
DbMigrationsConfiguration dbMgConfig = new Configuration()
{
ContextType = typeof(MyDbContext) //+++++CHANGE ME+++++
};
using (var databaseContext = new MyDbContext()) //+++++CHANGE ME+++++
{
try
{
var database = databaseContext.Database;
var migrationConfiguration = dbMgConfig;
migrationConfiguration.TargetDatabase =
new DbConnectionInfo(database.Connection.ConnectionString,
"System.Data.SqlClient");
var migrator = new DbMigrator(migrationConfiguration);
migrator.Update();
}
catch (AutomaticDataLossException adle)
{
dbMgConfig.AutomaticMigrationDataLossAllowed = true;
var mg = new DbMigrator(dbMgConfig);
var scriptor = new MigratorScriptingDecorator(mg);
string script = scriptor.ScriptUpdate(null, null);
throw new Exception(adle.Message + " : " + script);
}
}
}

Update Collection Value with Database in UWP(MVVM)

I have custom collection which contains student_id,student_name,student_mark.And having the table with same columns in the database as well. The design form have some controls for updating the existing student.
Temporarily all the updating operations are done with that custom collection.Lets assume we have 100 students data in collection and database. Any updating operation should reflect in the collection. But what my doubt is how do i update these values with the database before i close the application??
But when i open the application the collection should have all the values which have stored in the database.

But what my doubt is how do i update these values with the database
Firstly, you need to know how to do CRUD operations on MySQL database with uwp app. For this, please reference this sample.
Secondly, according to your description, you have built up a MVVM project to bind a collection data to the view. But you didn't have a data layer for this MVVM structure. For this, you need to create a class for data layer to do GRUD operations, and establish contact with this data service from ViewModel. More details please reference this article.
The class for data layer I wrote according to your description which contains how to read, update and delete data from mysql database is as follows:
public class Student
{
public int Student_id { get; set; }
public string Student_name { get; set; }
public string Student_mark { get; set; }
}
public class DataService
{
static string connectionString;
public static String Name = "Data Service.";
private static ObservableCollection<Student> _allStudents = new ObservableCollection<Student>();
public static ObservableCollection<Student> GetStudents()
{
try
{
string server = "127.0.0.1";
string database = "sakila";
string user = "root";
string pswd = "!QAZ2wsx";
connectionString = "Server = " + server + ";database = " + database + ";uid = " + user + ";password = " + pswd + ";SslMode=None;";
using (MySqlConnection connection = new MySqlConnection(connectionString))
{
connection.Open();
MySqlCommand getCommand = connection.CreateCommand();
getCommand.CommandText = "SELECT * FROM student";
using (MySqlDataReader reader = getCommand.ExecuteReader())
{
while (reader.Read())
{
_allStudents.Add(new Student() { Student_id = reader.GetInt32(0), Student_name = reader.GetString(1), Student_mark = reader.GetString(2) });
}
}
}
}
catch (MySqlException sqlex)
{
// Handle it :)
}
return _allStudents;
}
public static bool InsertNewStudent(Student newStudent)
{
// Insert to the collection and update DB
try
{
using (MySqlConnection connection = new MySqlConnection(connectionString))
{
connection.Open();
MySqlCommand insertCommand = connection.CreateCommand();
insertCommand.CommandText = "INSERT INTO student(student_id, student_name, student_mark)VALUES(#student_id, #student_name,#student_mark)";
insertCommand.Parameters.AddWithValue("#student_id", newStudent.Student_id);
insertCommand.Parameters.AddWithValue("#student_name", newStudent.Student_name);
insertCommand.Parameters.AddWithValue("#student_mark", newStudent.Student_mark);
insertCommand.ExecuteNonQuery();
return true;
}
}
catch (MySqlException sqlex)
{
return false;
}
}
public static bool UpdateStudent(Student Student)
{
try
{
using (MySqlConnection connection = new MySqlConnection(connectionString))
{
connection.Open();
MySqlCommand insertCommand = connection.CreateCommand();
insertCommand.CommandText = "Update student Set student_name= #student_name, student_mark=#student_mark Where student_id =#student_id";
insertCommand.Parameters.AddWithValue("#student_id", Student.Student_id);
insertCommand.Parameters.AddWithValue("#student_name", Student.Student_name);
insertCommand.Parameters.AddWithValue("#student_mark", Student.Student_mark);
insertCommand.ExecuteNonQuery();
return true;
}
}
catch (MySqlException sqlex)
{
// Don't forget to handle it
return false;
}
}
public static bool Delete(Student Student)
{
try
{
using (MySqlConnection connection = new MySqlConnection(connectionString))
{
connection.Open();
MySqlCommand insertCommand = connection.CreateCommand();
insertCommand.CommandText = "Delete from sakila.student where student_id =#student_id";
insertCommand.Parameters.AddWithValue("#student_id", Student.Student_id);
insertCommand.ExecuteNonQuery();
return true;
}
}
catch (MySqlException sqlex)
{
return false;
}
}
}
For updating the database in TwoWay binding way, we can implement is by invoking the data updating method in
PropertyChanged event as follows:
void Person_OnNotifyPropertyChanged(Object sender, PropertyChangedEventArgs e)
{
organization.Update((StudentViewModel)sender);
}
For the completed demo you can download here.

LINQ Database

I have a system that supports multiple products. Each product has its own database with the same exact schema.
When I pass in the connection string as a parameter to my Data Context constructor it always uses the default database listed in the connection string, or the default database of the user connecting if I do not provide an Initial Catalog in the connection string.
I would like to be able to have the system utilize a database without having to change the connection string and by passing in the database name as a parameter.
Here is an example of the code I am using:
class Program
{
static void Main(string[] args)
{
var d = new Data("Data Source=(LOCAL);Initial Catalog=Database1;Integrated Security=true;");
var d1 = new Data("Data Source=(LOCAL);Initial Catalog=Database2;Integrated Security=true;");
Console.ReadLine();
}
}
internal class Data
{
public Data(string connection)
{
using (var ctx = new DataClassDataContext(connection))
{
var query = from c in ctx.MyTable select c;
try
{
Console.WriteLine(query.Count());
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
}
If this code gets executed, then the first result will pull from Database1 and the second result will pull from Database2. I would like it to have the ability to pull from a database that is not provided in the connection string. The reason for this is because the database could change based on a specific scenario but the connection string will remain the same.
Here is an example of what I am using to "fake" it, but I don't really think this is the best solution for this:
class oConnection
{
public string Server { get; set; }
public string Database { get; set; }
public bool IntegratedSecurity { get; set; }
public string UserName { get; set; }
public string Password { get; set; }
}
class Program
{
static void Main(string[] args)
{
var d = new Data(new oConnection
{
Database = "Database1",
Server = "(Local)",
IntegratedSecurity = true
});
var d1 = new Data(new oConnection
{
Database = "Database2",
Server = "(Local)",
IntegratedSecurity = true
});
Console.ReadLine();
}
}
internal class Data
{
private static string BuildConnection(oConnection connection)
{
var sb = new StringBuilder();
sb.Append("Data Source=" + connection.Server + ";Initial Catalog=" + connection.Database + ";");
if(connection.IntegratedSecurity)
{
sb.Append("Integrated Security=true;");
}
else
{
sb.Append("user id=" + connection.UserName + ";password=" + connection.Password);
}
return sb.ToString();
}
public Data(oConnection connection)
{
using (var ctx = new DataClassDataContext(BuildConnection(connection)))
{
var query = from c in ctx.MyTable select c;
try
{
Console.WriteLine(query.Count());
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
}
Another note: the goal of this is really to be able to support not having multiple different connection strings when running queries that will span across multiple databases. For example: If I want to query the account records from a database and then query some sort of lookup data from another database, I would have to create a new connection string for the context.
Any help would be appreciated.
Thanks

Use the constructor that receives System.Data.IDbConnection connection. You can use the same connection string, and call connection.ChangeDatabase("mydb") before passing it to the constructor. Alternatively you can add a new constructor on the partial class, so the calling call doesn't has to deal with that.

you can use the SqlConnectionStringBuilder
class