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C# EF, refresh context

I'm creating an app that should work with various sqlite databases (with same structure) and I want to be able to open and close different databases. I use EF6 and I just can't figure out how to open a different database file (and make EF to reload and use data from new file). There are many questions regarding this but none of them work for me.
this is my dbContext generated by EF
public partial class mainEntities : DbContext
{
public mainEntities()
: base("name=mainEntities")
{
}
...
}
this is how I use and try to update my context
class Db
{
private static mainEntities myDbInstance;
public static mainEntities MyDbInstance
{
get
{
if (myDbInstance == null)
{
myDbInstance = new mainEntities();
}
return myDbInstance;
}
}
public static void UpdateConnectionString(string pth)
{
StringBuilder sb = new StringBuilder();
sb.Append("metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;");
sb.Append("provider=System.Data.SQLite.EF6;");
sb.Append("provider connection string=");
sb.Append("'");
sb.Append("datetime format=JulianDay;");
sb.Append("foreign keys=True;");
sb.Append("data source=");
sb.Append(pth);
sb.Append("'");
var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
var connectionStringsSection = (ConnectionStringsSection)config.GetSection("connectionStrings");
connectionStringsSection.ConnectionStrings["mainEntities"].ConnectionString = sb.ToString();
connectionStringsSection.ConnectionStrings["mainEntities"].ProviderName = "System.Data.EntityClient";
config.Save();
ConfigurationManager.RefreshSection("connectionStrings");
Properties.Settings.Default.Save();
Properties.Settings.Default.Reload();
//reset context - does not work
MyDbInstance.Dispose();
myDbInstance = null;
}
}
I am able to update the connectionString,
var conn_str = System.Configuration.ConfigurationManager.ConnectionStrings["mainEntities"].ConnectionString;
returns correct string after I change database file, but data is loaded from the original one.
EDIT:
I check if the connection changed with simple WPF GUI
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void refresh_labels()
{
var conn_str = System.Configuration.ConfigurationManager.ConnectionStrings["mainEntities"].ConnectionString;
var rows_count =
(from d in Db.MyDbInstance.TagsFiles
select d).Count();
label1.Content = conn_str.Split(';')[4];
label2.Content = rows_count;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
String DbFileName1 = #"c:\tmp\db1.db3";
String DbFileName2 = #"c:\tmp\db2.db3";
var conn_str = System.Configuration.ConfigurationManager.ConnectionStrings["mainEntities"].ConnectionString;
if (conn_str.Contains(DbFileName1))
{
Db.UpdateConnectionString(DbFileName2);
}
else
{
Db.UpdateConnectionString(DbFileName1);
}
refresh_labels();
}
}

How to call object from one class to another in C#

I have a problem that I just can't solve on my own. I am new to programming and I would appreciate if you could help me with this issue:
I have a class I would like to inherit from:
namespace rsDeployer.Common.SQLServerCommunication
{
public class RSDatabaseConnectionCreator: LoggerBase
{
public RSProfile profile;
public RSDatabaseConnectionCreator(RSProfile profile)
{
this.profile = profile;
}
public SqlConnection CreateConnection(RSDatabaseNames DatabaseName, bool UseWindowsAuthentication, bool testConnection = false)
{
var connectionString = BuildRSDatabaseConnectionString(DatabaseName, UseWindowsAuthentication);
if (testConnection)
{
return IsConnectionAvailable(connectionString) ? new SqlConnection(connectionString) : null;
}
return new SqlConnection(connectionString);
}
}
}
and I would like to call CreateConnection() in another class to inject to methods to allow me to open connection and then execute scripts.
Edit 1 - class I would like to have it injected to.
public void QueryExecution(string SQLQuery)
{
//here's where I would like to inject it
SqlCommand command = new SqlCommand(SQLQuery, conn);
var file = new StreamWriter(#"D:\Project\rsDeployer\ImportedQuery.txt");
file.WriteLine(command);
file.Close();
}
If this question is way to silly to deserve answer would you just point in the direction where I should read about it?
I hope this question is well asked and clear.
Thanks in advance.

Like this,
public void QueryExecution(string SQLQuery)
{
RSProfile profile = new RSProfile();
RSDatabaseConnectionCreator instance = new RSDatabaseConnectionCreator(profile);
SqlConnection conn = instance.CreateConnection(...);
SqlCommand command = new SqlCommand(SQLQuery, conn);
var file = new StreamWriter(#"D:\Project\rsDeployer\ImportedQuery.txt");
file.WriteLine(command);
file.Close();
conn.Close();
}
You also told that you want to inherit from this class, here is another approach,
public class RSDatabaseConnectionCreator : LoggerBase
{
public virtual object CreateConnection() // by virtual you can override it.
{
return new object();
}
}
public class AnotherClass : RSDatabaseConnectionCreator {
public AnotherClass() {
CreateConnection(); // by inheriting RSDatabaseConnectionCreator , you can reach public functions.
}
public override object CreateConnection() // or you can override it
{
// here might be some user Login check
return base.CreateConnection(); // then you open connection
}
}
Hope helps,

Hope this is what you are requesting for
public class ClassX
{
private RSProfile _rsprofile;
RSDatabaseConnectionCreator _dbConnectionCreator;
private SqlConnection _sqlConnection;
public ClassX()
{
_rsProfile = xxx; // Get the RSProfile object
_dbConnectionCreator = new RSDatabaseConnectionCreator (_rsProfile);
RSDatabaseNames databaseName = yyy; // get the RSDatabaseNames
var useWindowsAuthentication = true;
var testConnection = false;
_sqlConnection = _dbConnectionCreator.CreateConnection(databaseName,useWindowsAuthentication ,testConnection );
}
}

This is how you do it. Apologies for a major blunder in the earlier answer. This one has the connection surrounded by a using.
namespace rsDeployer.Common.SQLServerCommunication
{
public class ConsumerClass
{
public void QueryExecution(string SQLQuery)
{
var profile = new RsProfile();
var rsConnectionCreator = new RSDatabaseConnectionCreator(profile);
using(var sqlConnection = rsConnectionCreator.CreateConnection(...Parameters here...)){
SqlCommand command = new SqlCommand(SQLQuery, sqlConnection );
}
var file = new StreamWriter(#"D:\Project\rsDeployer\ImportedQuery.txt");
file.WriteLine(command);
file.Close();
}
}
}

You can inject the connection creator into the consumer class through the constructor.
public class Consumer
{
private RSDatabaseConnectionCreator _connectionCreator;
// Constructor injection
public Consumer (RSDatabaseConnectionCreator connectionCreator)
{
_connectionCreator = connectionCreator;
}
public void QueryExecution(string SQLQuery)
{
using (var conn = _connectionCreator.CreateConnection(dbName, true, true)) {
if (conn != null) {
...
}
}
}
}
Note: The using statement automatically closes the connection.
Usage
var connectionCreator = new RSDatabaseConnectionCreator(profile);
var consumer = new Consumer(connectionCreator);
consumer.QueryExecution(sqlQuery);
If you want to inject the connection creator at each call of QueryExecution, you can inject it directly into the method as an additional parameter, instead.
public void QueryExecution(string SQLQuery, RSDatabaseConnectionCreator connectionCreator)
{
using (var conn = connectionCreator.CreateConnection(dbName, true, true)) {
if (conn != null) {
...
}
}
}
Usage
var connectionCreator = new RSDatabaseConnectionCreator(profile);
var consumer = new Consumer();
consumer.QueryExecution(sqlQuery, connectionCreator);

Entitiy framework and sqlite as file path not working

I have been trying Browse a sqlite db file and read data using Entity framework .
But following way does not work
I am initiating the MydbContext with sqlite file path
eg
using (var sourceContext = new MydbContext(#"D:\test\data.sqlite"))
{
var a= sourceContext.MyModel.ToList();
}
public MydbContext(string path)
: base(GetConnectionString(path))
{
Configuration.LazyLoadingEnabled = false;
}
public static string GetConnectionString(string path)
{
var entityConnectionString = new EntityConnectionStringBuilder
{
Metadata = "res://*",
Provider = "System.Data.SQLite.EF6",
ProviderConnectionString = sqlLiteConnectionString,
}.ConnectionString;
}
Please suggest if there is a proper way to achieve this using sqlite and ef.

Got the answer from comments
private static SQLiteConnection GetConnectionString(string path)
{
var con= new SQLiteConnection()
{
ConnectionString =
new SQLiteConnectionStringBuilder()
{ DataSource = path, ForeignKeys = true,BinaryGUID = false }
.ConnectionString
};
return con;
}

EF Core - Add new tables to database During Runtime

I have an asp.net core project which needs to be able to support plugins at runtime, and as a consequence, I need to generate database tables based on what has been plugged in. The plugins are each divided in separate projects and they have have their own DbContext class. The plugins to be used are not known during compile-time, only at runtime.
Now in EF Core I thought that there would be a method like "UpdateDatabase" where you can just add tables to the existing database, but I was wrong. Is there a way to accomplish this? I was able to generate a separate database for each of the plugins, but that wasn't quite what I had in mind..I needed all tables in one database.
Here's the code for the "HRContext" plugin:
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.EntityFrameworkCore;
using Plugins.HR.Models.Entities;
namespace Plugins.HR.Contexts
{
public class HrContext : DbContext
{
public HrContext()
{
}
public HrContext(DbContextOptions<HrContext> contextOptions) : base(contextOptions)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.HasDefaultSchema("HR");
base.OnModelCreating(modelBuilder);
}
public DbSet<Address> Address { get; set; }
public DbSet<Attendance> Attendance { get; set; }
public DbSet<Department> Departments { get; set; }
public DbSet<Employee> Employees { get; set; }
public DbSet<JobTitle> JobTitles { get; set; }
}
}
Here's another piece of code for the "CoreContext" plugin:
using System;
using System.Collections.Generic;
using System.Text;
using Core.Data.Models;
using Microsoft.EntityFrameworkCore;
namespace Core.Data.Contexts
{
public class CoreContext : DbContext
{
public CoreContext()
{
}
public CoreContext(DbContextOptions<CoreContext> contextOptions) : base(contextOptions)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.HasDefaultSchema("Core");
base.OnModelCreating(modelBuilder);
}
public DbSet<Test> Tests { get; set; }
}
}
My ConfigureServices method in Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<CoreContext>(options => options.UseSqlServer("Data source = localhost; initial catalog = Company.Core; integrated security = true;"))
.AddDbContext<HrContext>(options => options.UseSqlServer("Data source = localhost; initial catalog = Company.HR; integrated security = true;"));
// Add framework services.
services.AddMvc();
}
If I try to change the connection string to be the same, sooner or later I will get an error that says that the table for one plugin does not exist. I tried "EnsureCreated" but that didn't work too.

I had the same issue. See my solution on GitHub a few days ago, here: EF Core Issue #9238
What you need is something like the following:
// Using an interface, so that we can swap out the implementation to support PG or MySQL, etc if we wish...
public interface IEntityFrameworkHelper
{
void EnsureTables<TContext>(TContext context)
where TContext : DbContext;
}
// Default implementation (SQL Server)
public class SqlEntityFrameworkHelper : IEntityFrameworkHelper
{
public void EnsureTables<TContext>(TContext context)
where TContext : DbContext
{
string script = context.Database.GenerateCreateScript(); // See issue #2943 for this extension method
if (!string.IsNullOrEmpty(script))
{
try
{
var connection = context.Database.GetDbConnection();
bool isConnectionClosed = connection.State == ConnectionState.Closed;
if (isConnectionClosed)
{
connection.Open();
}
var existingTableNames = new List<string>();
using (var command = connection.CreateCommand())
{
command.CommandText = "SELECT table_name from INFORMATION_SCHEMA.TABLES WHERE table_type = 'base table'";
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
existingTableNames.Add(reader.GetString(0).ToLowerInvariant());
}
}
}
var split = script.Split(new[] { "CREATE TABLE " }, StringSplitOptions.RemoveEmptyEntries);
foreach (string sql in split)
{
var tableName = sql.Substring(0, sql.IndexOf("(", StringComparison.OrdinalIgnoreCase));
tableName = tableName.Split('.').Last();
tableName = tableName.Trim().TrimStart('[').TrimEnd(']').ToLowerInvariant();
if (existingTableNames.Contains(tableName))
{
continue;
}
try
{
using (var createCommand = connection.CreateCommand())
{
createCommand.CommandText = "CREATE TABLE " + sql.Substring(0, sql.LastIndexOf(";"));
createCommand.ExecuteNonQuery();
}
}
catch (Exception)
{
// Ignore
}
}
if (isConnectionClosed)
{
connection.Close();
}
}
catch (Exception)
{
// Ignore
}
}
}
}
Then at the end of Startup.Configure(), I resolve an IEntityFrameworkHelper instance and use that with an instance of DbContext to call EnsureTables().
One issue is I need to still account for the parts of the script which are not CREATE TABLE statements. For example, the CREATE INDEX statements.
I requested they give us a clean solution, for example: add a CreateTable<TEntity>() method to IRelationalDatabaseCreator. Not holding my breath for that though...
EDIT
I forgot to post the code for GenerateCreateScript(). See below:
using System.Text;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.EntityFrameworkCore.Migrations;
using Microsoft.EntityFrameworkCore.Storage;
public static class DatabaseFacadeExtensions
{
public static string GenerateCreateScript(this DatabaseFacade database)
{
var model = database.GetService<IModel>();
var migrationsModelDiffer = database.GetService<IMigrationsModelDiffer>();
var migrationsSqlGenerator = database.GetService<IMigrationsSqlGenerator>();
var sqlGenerationHelper = database.GetService<ISqlGenerationHelper>();
var operations = migrationsModelDiffer.GetDifferences(null, model);
var commands = migrationsSqlGenerator.Generate(operations, model);
var stringBuilder = new StringBuilder();
foreach (var command in commands)
{
stringBuilder
.Append(command.CommandText)
.AppendLine(sqlGenerationHelper.BatchTerminator);
}
return stringBuilder.ToString();
}
}
It's based on the code found here: EF Core Issue #2943

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);
}
}
}