Develop Reference

don't know Connection string parameter in C#

i am developing an application in C#,i have create database1.mdf by
right clicking on my project,add item
then creating a database.
my intial problem was,i was able to execute query correctly but those modification wasn't reflected in main database
finally after lot of surfing i changed copy to output directory to copy if newer but still i am not able to rectify my problem.
now i am feeling that i need to connect to sqlserver using connectionstring but i don't know username,servername,password etc...
can anyone help me please

if you want to connect database in csharp so visual studio will help you to connect with database
go to solution explorer right click on project and add new item and select service-base database click add.
Now Go to Server explorer look there is database with .mdf extension
expand it right click on table and create table your self.
After creating table you need connection string to connect your application to database.
you connection string look like this
string databaseFileName="Your database file with .mdf extension like database1.mdf";
string connectionString=#"Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\"+databaseFileName+";Integrated Security=True";
SqlConnection conn=new SqlConnection(connectionString);
conn.Open();
Console.writeLine(conn.State.ToString());/*this will show your database state is open or close.
Note:Here i am using visual studion 2013 other (LocalDB)\v11.0 this could be changed .

Connecting C# app with Oracle 10g: ORA-12154: TNS:could not resolve the connect identifier specified

I am a beginner in working with databases. I am trying to access Oracle10g database from a c# application. But when I do so i get this error:
ORA-12154: TNS:could not resolve the connect identifier specified"
I'm using the following code:
string oradb = "Data Source=ORCL;User Id=system;Password=goodbye;";
OracleConnection conn = new OracleConnection(oradb); // C#
conn.Open();
Is there an error in the connection string oradb?

Start the Visual Studio, open View menu + Server Explorer.
Right mouse click on Data Connection + Add Connection + Select Oracle Database
server Name : localhost or name of your machine, set username & password and click on Test Connection to verify the above parameters. Press OK if test is succeeds.
From properties windows you can obtain connection String and it should be look a like:
Data Source=localhost;Persist Security Info=True;User ID=scott;Password=***********;Unicode=True

Oracle is just stating that it can't find the database.
If you're running a local Express Edition database, you should be able to just use XE as an instance name, and everything should already be set up, otherwise you can most easily add it to tnsnames.ora.
To find the correct tnsnames.ora to change, you can try (from the command prompt)
tnsping ORCL
That will tell you which files Oracle is using to try to find the database. If tnsping is an unknown command, you may have to search for it and go to the correct place before running it.
One you found the correct tnsnames.ora, you need to add the instance ORCL to it. There should be an existing file with examples, the syntax of that file is too complex to answer here, if you need help, Oracle has quite extensive documentation.

This is a very common oracle error. Simply put, it means that you have named the database you wish to be connected to and Oracle doesn’t know who the heck you’re talking about. I suggest 6 Steps to fix ORA-12154:
Check instance name has been entered correctly in tnsnames.ora.
There should be no control characters at the end of the instance or database name.
All paranthesis around the TNS entry should be properly terminated
Domain name entry in sqlnet.ora should not be conflicting with full database name.
If problem still persists, try to re-create TNS entry in tnsnames.ora.
At last you may add new entries using the SQL*Net Easy configuration utility.
More informations on oracle site or here : http://turfybot.free.fr/oracle/11g/errors/ORA-12154.html

How to get the connection String from a database

I have created a database with SQL Server Management Studio, I would like to now use it in my C# application. I need the connection string?
Where can I find the connection string, and where is my database stored?
Do I have to publish it or something like that, or is it in my documents somewhere?
using (var conn = new SqlConnection("your connection string to the database"))
How do I obtain the connection string? Where can I find the connection string to copy paste into the above section?
How to I publish my database so that Visual Studio can pick it up? Then I can just pull the connection string of there?

The easiest way to get the connection string is using the "Server Explorer" window in Visual Studio (menu View, Server Explorer) and connect to the server from that window.
Then you can see the connection string in the properties of the connected server (choose the connection and press F4 or Alt+Enter or choose Properties on the right click menu).
Advanced connection string settings: when creating the connection, you can modify any of the advanced connection string options, like MARS, resiliency, timeot, pooling configuration, etc. by clicking on the "Advanced..." button on the bottom of the "Add connection" dialog. You can access this dialog later by right clicking the Data Connection, and choosing "Modify connection...". The available advanced options vary by server type.
If you create the database using SQL Server Management Studio, the database will be created in a server instance, so that, to deploy your application you'll have to make a backup of the database and deploy it in the deployment SQL Server. Alternatively, you can use a data file using SQL Server Express (localDB in SQL Server 2012), that will be easily distributed with your app.
I.e. if it's an ASP.NET app, there's an App_Datafolder. If you right click it you can add a new element, which can be a SQL Server Database. This file will be on that folder, will work with SQL Express, and will be easy to deploy. You need SQL Express / localDB installed on your machine for this to work.

A very simple way to retrieve a connection string, is to create a text file, change the extension from .txt to .udl.
Double-clicking the .udl file will open the Data Link Properties wizard.
Configure and test the connection to your database server.
Close the wizard and open the .udl file with the text editor of your choice and simply copy the connection string (without the Provider=<driver>part) to use it in your C# application.
sample udl file content
[oledb]
; Everything after this line is an OLE DB initstring
Provider=SQLNCLI11.1;Integrated Security=SSPI;Persist Security Info=False;User ID="";Initial Catalog=YOURDATABASENAME;Data Source=YOURSERVERNAME;Initial File Name="";Server SPN=""
what you need to copy from it
Integrated Security=SSPI;Initial Catalog=YOURDATABASENAME;Data Source=YOURSERVERNAME;
If you want to specify username and password you can adopt from other answers.
Tutorial: https://teusje.wordpress.com/2012/02/21/how-to-test-an-sql-server-connection/

Open SQL Server Management Studio and run following query. You will get connection string:
select
'data source=' + ##servername +
';initial catalog=' + db_name() +
case type_desc
when 'WINDOWS_LOGIN'
then ';trusted_connection=true'
else
';user id=' + suser_name() + ';password=<<YourPassword>>'
end
as ConnectionString
from sys.server_principals
where name = suser_name()

If you have installed and setup MS SQL Server and Management Studio, go to Visual Studio (Visual Studio not SQL Server Management Studio).
1] In Visual Studio go to Tools -> Connect to Database.
2] Under Server Name Select your Database Server Name (Let the list Populate if its taking time).
3] Under Connect to a Database, Select Select or enter a database name.
4] Select your Database from Dropdown.
5] After selecting Database try Test Connection.
6] If Test Connection Succeeds, Click Ok.
7] In Visual Studio go to View -> Server Explorer.
8] In Server Explorer window, Under Data Connections Select your Database. Right Click your Database -> Click Properties.
9] In Properties window you will see your Connection String.

On connectionstrings.com you can find the connection string for every DB provider. A connection string is built up with certain attributes/properties and their values. For SQL server 2008, it looks like this (standard, which is what you'll need here):
Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
on myServerAddress, write the name of your installed instance (by default it's .\SQLEXPRESS for SQL Server Express edition). Initial catalog = your database name, you'll see it in SSMS on the left after connecting. The rest speaks for itself.
edit
You will need to omit username and password for windows authentication and add Integrated Security=SSPI.

My solution was to use excel (2010).
In a new worksheet, select a cell, then:
Data -> From Other Sources -> From SQL Server
put in the server name, select table, etc,
When you get to the "Import Data" dialog,
click on Properties in the "Connection Properties" dialog,
select the "Definition" tab.
And there Excel nicely displays the Connection String for copying
(or even Export Connection File...)

If one uses the tool Linqpad, after one connects to a target database from the connections one can get a connection string to use.
Right click on the database connection.
Select Properties
Select Advanced
Select Copy Full Connection String to Clipboard
Result: Data Source=.\jabberwocky;Integrated Security=SSPI;Initial Catalog=Rasa;app=LINQPad
Remove the app=LinqPad depending on the drivers and other items such as Server instead of source, you may need to adjust the driver to suit the target operation; but it gives one a launching pad.

put below tag in web.config file in configuration node
<connectionStrings>
<add name="NameOFConnectionString" connectionString="Data Source=Server;Initial Catalog=DatabaseName;User ID=User;Password=Pwd"
providerName="System.Data.SqlClient" />
then you can use above connectionstring, e.g.
SqlConnection con = new SqlConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings["NameOFConnectionString"].ToString();

The sql server database will be stored by default in the following path
<drive>:\Program Files\Microsoft SQL Server\MSSQL.X\MSSQL\Data\
, where <drive> is the installation drive and X is the instance number (MSSQL.1 for the first instance of the Database Engine). Inorder to provide the connection string you should know what is the server name of the sql server database, where you have stored followed by instance of the database server.
Generally the server name will be like the ip address of the machine where the database is attached and the default instance will be SqlExpress
A connection string contains Data Source name i.e., server name, Initial catalog i.e., database name, user id i.e., login user id of the database, password i.e., login password of the database.

Easiest way my friends, is to open the server explorer tab on visual studio 2019 (in my case), and then try to create the connection to the database. After creating a succesful connection just right click on it and go to propierties. There you will find a string connection field with the correct syntax!...This worked for me because I knew my server's name before hand....just couldn't figure out the correct syntax to run my ef scaffold...

If you created Connection Manager in your project then you can simply pull the connection string from there.
String connection = this.dts.connections["<connection_manager_name>"];
And use this connection in:
using (var conn = new SqlConnection(connection))
Please correct me if I am wrong.

SqlConnection con = new SqlConnection();
con.ConnectionString="Data Source=DOTNET-PC\\SQLEXPRESS;Initial Catalog=apptivator;Integrated Security=True";

C# and SQLite: "no such table error" when using relative path?

I am having issues connecting to my sqlite database. The file is located in the application's folder. Here is the connection string
string path = "Data Source=MY.db";
I can get it to work if I use the absolute path, but it gives me a "table not found" error if I try to use a relative path. Any ideas?

You are opening up a different -- perhaps a new -- database that does not have said table. (Yes, SQLite will happily create a new database with the default connection settings.)
Make sure the correct database is opened. Remember, relative path is relative to the Current Working Directory, which is likely not that which is expected.
(The working directory is influenced from where, and how, the process is loaded. The working directory for a "Debug" session can be set under Project Settings / Debug / Start Options, for instance.)
Happy coding.
See also:
Make SQLite connection fail if database is missing? (deleted/moved)
Defining a working directory for executing a program (C#) (Shows how to set the current working directory to the directory containing the executing assembly.)
How do I get/set a winforms application's working directory?
Getting path relative to the current working directory?

This happened when you haven't saved the database and its table while using GUI Manager for SQLite .
Two solution;
1) Save your database and its table with CTR+S in GUI Manager
2) Or Simply Just close your GUI manager of SQlite and save all .
Important ! I am using GUI manger for SQLITE (DB Browser for SQLITE) and its all about that.

I've had the same problem for both my windows application (C#) and web application (ASP.net). I usually use SQLite because I found it more easier, especially when I worked with connection strings. But the main obstacle for me was to put a relative path in my code, so I can publish it without worrying about being unable to find the database. I've tried many things(using "|Data Directory|", "~/", "./", ...), and none of them works until I found these solutions. It seems the code is working for me, but wonder if I'm using them right?!
Web Application:
SQLiteConnection sql_con = new SQLiteConnection("Data Source =" + Server.MapPath("~/") + "mydb.db; Version = 3; New = false;);
Windows App:
SQLiteConnection sql_con = new SQLiteConnection("Data Source =" + System.IO.Path.GetDirectoryName(Application.ExecutablePath) + "mydb.db; Version = 3; New = false; Read Only = true");

just replace your .database file into \bin\Debug in project folder, because in your case compiler creates DB file with same name but its totally empty 0bytes

Writing into excel file with OLEDB

Does anyone know how to write to an excel file (.xls) via OLEDB in C#? I'm doing the following:
OleDbCommand dbCmd = new OleDbCommand("CREATE TABLE [test$] (...)", connection);
dbCmd.CommandTimeout = mTimeout;
results = dbCmd.ExecuteNonQuery();
But I get an OleDbException thrown with message:
"Cannot modify the design of table
'test$'. It is in a read-only
database."
My connection seems fine and I can select data fine but I can't seem to insert data into the excel file, does anyone know how I get read/write access to the excel file via OLEDB?

I was also looking for and answer but Zorantula's solution didn't work for me.
I found the solution on http://www.cnblogs.com/zwwon/archive/2009/01/09/1372262.html
I removed the ReadOnly=false parameter and the IMEX=1 extended property.
The IMEX=1 property opens the workbook in import mode, so structure-modifying commands (like CREATE TABLE or DROP TABLE) don't work.
My working connection string is:
"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=workbook.xls;Mode=ReadWrite;Extended Properties=\"Excel 8.0;HDR=Yes;\";"

You need to add ReadOnly=False; to your connection string
Provider=Microsoft.Jet.OLEDB.4.0;Data Source=fifa_ng_db.xls;Mode=ReadWrite;ReadOnly=false;Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=1\";

I also had the same problem. Only remove the extended property IMEX=1. That will solve your problem. Your table will be created in your Excel file...

A couple questions:
Does the user that executes your app (you?) have permission to write to the file?
Is the file read-only?
What is your connection string?
If you're using ASP, you'll need to add the IUSER_* user as in this example.

How do I check the permissions for writing to an excel file for my application (I'm using excel 2007)?
The file is not read only, or protected (to my knowledge).
My connection String is:
"Provider=Microsoft.Jet.OLEDB.4.0;Data
Source=fifa_ng_db.xls;Mode=ReadWrite;Extended
Properties=\"Excel
8.0;HDR=Yes;IMEX=1\""

Further to Michael Haren's answer. The account you will need to grant Modify permissions to the XLS file will likely be NETWORK SERVICE if this code is running in an ASP.NET application (it's specified in the IIS Application Pool). To find out exactly what account your code is running as, you can do a simple:
Response.Write(Environment.UserDomainName + "\\" + Environment.UserName);

I was running under ASP.NET, and encountered both "Cannot modify the design..." and "Cannot locate ISAM..." error messages.
I found that I needed to:
a) Use the following connection string:
Provider=Microsoft.Jet.OLEDB.4.0;Mode=ReadWrite;Extended Properties='Excel 8.0;HDR=Yes;';Data Source=" + {path to file};
Note I too had issues with IMEX=1 and with the ReadOnly=false attributes in the connection string.
b) Grant EVERYONE full permissions to the folder in which the file was being written. Normally, ASP.NET runs under the NETWORK SERVICE account, and that already had permissions. However, the OleDb code is unmanaged, so it must run under some other security context. (I am currently too lazy to figure out which account, so I just used EVERYONE.)