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How to pass ConnectionString parameters with variables?

I have a ConnectionString and I want to pass it values (DataSource, Database, User ID, Password) with values from a .txt file and I need to read them, then pass them to the connectionString but I'm very confused how should I do this.
In my program I have a Helper Class to return the connectionString
public static class Helper
{
public static string ConnectionString(string name)
{
return ConfigurationManager.ConnectionStrings[name].ConnectionString;
}
}
This is how I call the connectionString so I can access the database data
using (IDbConnection connection = new System.Data.SqlClient.SqlConnection(Helper.ConnectionString("Hotel")))
{
connection.Execute($"INSERT INTO dbo.Registos_Cancelados(Nome, Telemovel, Data) VALUES(#Nome, #Telemovel, #Data)", new { Nome = nome, Telemovel = telemovel, Data = data });
}
I have a text file with the values
"DataSourceName"
"DataBaseName"
"User IDName"
"PasswordName"
And I want them in the connection string.
<connectionStrings>
<add name="Hotel" connectionString="DataSource="DataSourceName";Database="DatabaseName";User Id="UserIdName";Password="PasswordName""
providerName="System.Data.SqlClient" />
</connectionStrings>

You're using SqlClient, so: your best bet here is SqlConnectionStringBuilder:
var cb = new SqlConnectionStringBuilder(theBaseString);
cb.DataSource = dataSourceName;
cb.InitialCatalog = dataBaseName;
cb.UserID = userId;
cb.Password = password;
var connectionString = cb.ConnectionString;
If you don't have a template string (theBaseString), just use new SqlConnectionStringBuilder() instead.
The advantage of using SqlConnectionStringBuilder here is that it knows all about the escaping rules for non-trivial values, reserved characters, etc.

You can format your connection string like below to pass the necessary values like dbname later.
<connectionStrings>
<add name="Hotel" connectionString="DataSource={0};Database={1};User Id={2};Password={3}"
providerName="System.Data.SqlClient" />
</connectionStrings>
After that in your Helper class, return the formatted connection string with the values that you read from txt file.
public static string ConnectionString(string name)
{
var dataSourceName = "...";
var dbName = "...";
var userId = "...";
var password = "...";
var connectionString = ConfigurationManager.ConnectionStrings[name].ConnectionString;
return string.Format(connectionString, dataSourceName, dbName, userId, password);
}

How to build connection string from existing connection for new database created dynamically?

I have query to dynamically create database.
private void ExecuteNonQuery(string sql)
{
using (var connection = new SqlConnection(_connectionString))
{
connection.Open();
SqlCommand command = connection.CreateCommand();
command.CommandText = sql;
command.ExecuteNonQuery();
}
}
private void CreateDatabase(string databaseName)
{
try
{
ExecuteNonQuery($"CREATE DATABASE {databaseName}");
}
catch (Exception e)
{
throw new Exception($"Can't create database '{databaseName}'");
}
}
Database will be created using my existing connection , But I need to create connection string for this new database to run migration and for various other purposes.
How is it possible ?
Update
Its actually for purpose where users can fill a form to create a new database where they can give their existing connection string or if they don't have one in hand we build it for them

use this function to get a connection to the new database:
private SqlConnection NewDatebaseConnection(string databaseName)
{
SqlConnection connection = new SqlConnection(_connectionString);
connection.ChangeDatabase(databaseName);
return SqlConnection;
}

To save new connection, you can use ConnectionStringBuilder with existing connection, change the name of database and save it to app.config.
1.Helper method to get connection string:
string GetConnectionString(string name) =>
ConfigurationManager.ConnectionStrings[name].ConnectionString;
2.Helper method which saves new connection string to app.config:
void CreateNewConnectionString(string baseName, string newName, string newDatabaseName)
{
// Get the connection string a new connection will be based on
string baseConnString =
ConfigurationManager.ConnectionStrings[baseName].ConnectionString;
// For simplicity of manipulations with connection strings,
// we use SqlConnectionStringBuilder, passing it an existing connection string
var connBuilder = new SqlConnectionStringBuilder(baseConnString);
// Change existing database name to the new database name
connBuilder.InitialCatalog = newDatabaseName;
// Create new settings, holding our new connection string
var newConnection = new ConnectionStringSettings(newName, connBuilder.ToString());
// Save new connection string
var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.ConnectionStrings.ConnectionStrings.Add(newConnection);
config.Save(ConfigurationSaveMode.Modified);
}
3.Usage
private void CreateDatabase(string databaseName)
{
try
{
// Create database using "main" connection string
ExecuteNonQuery($"CREATE DATABASE {databaseName}", "main");
// Create new connection string "my_db" based on "main"
CreateNewConnectionString("main", "my_db", databaseName);
}
catch (Exception e)
{
throw new Exception($"Can't create database '{databaseName}'");
}
}

If you are using EF, you should have a context to work with, something like the following:
public class MyContext : DbContext
{
public MyContext():base("myConnectionStringName")
{
}
}
The constructor has a parameter that specifies connection name or a connection string. So, you can obtain a context for any connections string you want:
using (var db = new MyContext("connection_string_containing_new_db")
{
// do stuff with the context
}
You should consider using a factory that builds such contexts:
class MyContextFactory
{
MyContext CreateContextForDatabase(string dbName)
{
var builder = new SqlConnectionStringBuilder();
builder["Data Source"] = "server\\instance";
builder["integrated Security"] = true;
builder["Initial Catalog"] = dbName;
return new new MyContext(builder.ConnectionString);
}
}
The code uses SqlConnectionStringBuilder to construct (from scratch) the connection string. An alternative is to parse a static connection string using var builder = new SqlConnectionStringBuilder(staticConnectionString) and only change the Initial Catalog.

Entity Framework set connection string at runtime

I have been trying to get this work for last couple of days with no success.
This is what I have done so far.
string providerName = "System.Data.SqlClient";
string serverName = serverIPAddress;
string databaseName = myDBName;
SqlConnectionStringBuilder sqlBuilder = new SqlConnectionStringBuilder();
sqlBuilder.DataSource = serverName;
sqlBuilder.InitialCatalog = databaseName;
sqlBuilder.PersistSecurityInfo = true;
sqlBuilder.MultipleActiveResultSets = true;
sqlBuilder.UserID = "sa";
sqlBuilder.Password = saPassword;
string providerString = sqlBuilder.ToString();
EntityConnectionStringBuilder entityBuilder = new EntityConnectionStringBuilder();
entityBuilder.Provider = providerName;
entityBuilder.ProviderConnectionString = providerString;
entityBuilder.Metadata = "res://*/TUModel.myModel.csdl|res://*/TUModel.myModel.ssdl|res://*/TUModel.myModel.msl";
myEntities ctx = new myEntities(entityBuilder.ConnectionString);
The constructor in entity class look like
public myEntities(string connectionString) : base("name=myEntities")
{
}
When I run there is no error. However if I delete 'myEntities' connection string from app.config, then it throws exception. If I leave it as it is then it ignores the connection string in the code and use the one in app.config.
Any help would be greatly appreciated.

Your context constructor isn't passing your connection string in, instead it is passing through a fixed value of name=myEntities. Change it to this:
public myEntities(string connectionString) : base(connectionString)
{
}

error when trying to programatically build connection string for EF 6

I am using EF ver 6 and I am trying to build my connection string programatically as follows:
public GlContext() : base(ConnectionString()) { }
private static string ConnectionString()
{
SqlConnectionStringBuilder sqlBuilder = new sqlConnectionStringBuilder();
sqlBuilder.DataSource = "myserver";
sqlBuilder.InitialCatalog = "GLPROD";
sqlBuilder.PersistSecurityInfo = true;
sqlBuilder.IntegratedSecurity = false;
sqlBuilder.MultipleActiveResultSets = true;
sqlBuilder.UserID = "user";
sqlBuilder.Password = "pwd";
sqlBuilder.ApplicationName = "EntityFramework";
EntityConnectionStringBuilder entityBuilder = new EntityConnectionStringBuilder();
entityBuilder.ProviderConnectionString = sqlBuilder.ToString();
entityBuilder.Provider = "System.Data.SqlClient";
return entityBuilder.ToString();
}
When trying to use GlContext I get this error:
keyword not supported: 'provider'
I have spent hours trying to figure out why this code would not work... if I load it from app.config then it works well. Any suggestion is appreciated.
Thanks

EntityConnectionStringBuilder should be used for EDMX model and for Code First model (DbContext based ones) you should use SqlConnectionStringBuilder.

change connection string in class application at runtime?

I have class application that uses ado.net to connect to Sqlite database. The application uses the db to store some data and the db may be changed at run time. The user may make backups of the db and change the location, but in this case i need to know how to change the connection string.
I have tried this code but it didn't work:
string conn =
#"metadata=res://*/KzDm.csdl|res://*/KzDm.ssdl|res://*/KzDm.msl;" +
#"provider=System.Data.SQLite;" +
#"provider connection string=" +
#""" +#"Data Source=" +
#"F:\My Own programs\KrarZara2\KZ\KZ\Kzdb.s3db" +
#""";
Entities ent = new
Entities(conn);
this error "Keyword not supported: 'data source'."
happen at this line
public Entities(string connectionString) : base(connectionString, "Entities")

i write that and it worked with me
EntityConnectionStringBuilder conn = new EntityConnectionStringBuilder();
conn.Metadata = #"res://*/KzDm.csdl|res://*/KzDm.ssdl|res://*/KzDm.msl";
conn.Provider = "System.Data.SQLite";
conn.ProviderConnectionString = #"data source=F:\My Own programs\KrarZara2\KZ\KZ\KrarDS.krar;Version=3;";
EntityConnection entity = new EntityConnection(conn.ConnectionString);
using (DmEnt ent = new DmEnt(entity))
{
var parcel = ent.Parcels.SingleOrDefault(d => d.id == 1);
var pparcc = ent.Parcels.Select(d => d.id == 2);
Parcel r = new Parcel();
r.ParcelNumber = "11ju";
r.Area = 8787;
ent.AddToParcels(r);
ent.SaveChanges();
}
Dm ent is the entity model in edmx ado.net

wrong line order, should be:
#""" +
#"Data Source=" +

I'd actually surprised that connection string works at all. In addition, it would be simpler to use string.Format to build this connection string:
var filename = #"F:\My Own programs\KrarZara2\KZ\KZ\Kzdb.s3db";
var connString = string.Format("Data Source={0};UseUTF16Encoding=True;", filename );
using( var conn = new SQLiteConnection( connString ) )
{
...
}
First, you would replace UseUTF16Encoding with the proper value for your setup. Second, note that the file path in the connection string is not surrounded by quotation marks.
If you are looking for a means to swap Sqlite data files at runtime you might look at this blog entry:
SQLite and Entity Framework 4
A summary of the solution is to parse the Entity framework connection string, change the data file and then reset it:
public static string RedirectedEntityFrameworkConnectionString(string originalConnectionString, string databaseFile, string password)
{
// Parse the Entity Framework connection string.
var connectionStringBuilder = new EntityConnectionStringBuilder(originalConnectionString);
if (connectionStringBuilder.Provider != "System.Data.SQLite")
{
throw new ArgumentException("Entity Framework connection string does not use System.Data.SQLite provider.");
}
// Parse the underlying provider (SQLite) connection string.
var providerConnectionStringBuilder = new SQLiteConnectionStringBuilder(connectionStringBuilder.ProviderConnectionString);
// Redirect to the specified database file, and apply encryption.
providerConnectionStringBuilder.DataSource = databaseFile;
providerConnectionStringBuilder.Password = password;
// Rebuild the Entity Framework connection string.
connectionStringBuilder.ProviderConnectionString = providerConnectionStringBuilder.ConnectionString;
return connectionStringBuilder.ConnectionString;
}
To use, you would do something like:
const string OriginalConnectionString = "..."; // (Copy out of app.config)
var connectionString = RedirectedEntityFrameworkConnectionString(OriginalConnectionString, myFileName, null);
using (var context = new MyEntities(connectionString))
{
...
}