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C# database file application on another pc

I am trying to make a simple database application. It is just writing and reading from local database file using c# winform, but when i move the application folder to another pc, it comes with error. I thought it is just some dumb mistake with connstring or file accesses but when i click continue and the Application starts, there is even nothing loaded in combo boxes (which should be filled normally, without using any database stuff). Sorry for my English and thanks for response.
I cannot post image because i am new here but the exception says among other text this:
error 50 - local database runtime error occurred. The specified
LocalDB instance does not exist.

The solution really depends on what is your application's design.
Centralized Database:
If your application is supposed to use the centralized database - meaning multiple c# winform applications connect with same database.
Then you will have to make sure that the database server's IP address / machine name / Identifier is mentioned as "Data Source" in the connection string.
For ex. below connection string shows, how you will connect to database if windows authentication is to be used for connection. You will have to replace Data Source as your IP address and Initial Catalog with the database name
Data Source=your-server-address;Initial Catalog=your-database;Integrated Security=TRUE;
Local Database:
If your application is supposed to use local database i.e. for every c# winforms application user, there will be local database on his machine,
Then you will have to make sure that the required components (i.e. SQL Express, SQL or any other database server you want to use) are installed.
Hope this clarifies.

Check your LocalDB connection string and point it to the right file location as you can see below (taken from here). Its path is now different as you moved your application (AttachDBFilename attribute)
<connectionStrings>
<add name="DefaultConnection" connectionString="Data Source=
(LocalDb)\MSSQLLocalDB;Initial Catalog=aspnet-MvcMovie-fefdc1f0-bd81-4ce9-b712-
93a062e01031;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\aspnet-
MvcMovie-fefdc1f0-bd81-4ce9-b712-93a062e01031.mdf"
providerName="System.Data.SqlClient" />
</connectionStrings>

First chance exception of 'System.Data.EntityException'. The underlying provider failed on Open

I've been given a site that was created by someone else and I'm now trying to test it. I can compile the system without any problems but when I try to log in to the website, I get the error:
"EntityException occured. A first chance exception of type 'System.Data.EntityException' occured in System.Data.Entity.dll. Additional info: The underlying provider failed on Open."
Furthermore, if I dig deeper, I see an InnerException of Cannot open database \"MyDB\" requested by the login. The login failed. Login failed for user 'name\\owner'.
I've read similar problems on the web and it seems like its a problem with database connections? I've tried multiple 'solutions' that include messing around with the connectionString but nothing works.
What I think the system wants to do is connect to a .mdf located in a separate project's App_Data. Anyway, here's the connectionString code that I received originally:
add name="NameServiceContext"
connectionString="Server=tcp:qiu5vg5yhv.database.windows.net,1433;Database=MyDB;User ID=MYID;Password=MYPASS;Trusted_Connection=False;Encrypt=True;Connection Timeout=30;"
providerName="System.Data.SqlClient"
Quick question, what is the tcp:...... stuff? I'm assuming it was generated somehow, but how?
I've tried 'fixing' the problem and ended up with something like this:
add name="NameServiceContext"
connectionString="data source=./SQLEXPRESS;AttachDbFilename=C:\Users\owner\Documents\MyERP\App_Data\MyDB.mdf;Integrated Security=True;Connect Timeout=30;"
providerName="System.Data.SqlClient"
Both methods give the same errors and I'm out of ideas. How would I go about fixing this?
Also, when I connect to a db via tools>connect to database > MS SQL db file, I get an option between 2 data sources, ./SQLEXPRESS and (LocalDB)\v11.0. Do I have to include both of them? If so, how?

The original connection string refers to a Microsoft Azure instance. A typical connection string to Azure looks like:
Server=tcp:[serverName].database.windows.net;Database=myDataBase;User ID=[LoginForDb]#[serverName];Password=myPassword;Trusted_Connection=False;Encrypt=True;
Your server name is qiu5vg5yhv.database.windows.net. Most likely your credentials are incorrect.

It is as Andrew said, you don't seem to have access to the actual database. Simply download either "SQL Server Management Studio" or "SQL Server Management Studio Express" (depend on which version of database you are using) and try to connect.
If you connect successfully, check if you can query the database of your project.
If you connect unsuccessfully, contact your system admin to arrange access.
If you want to understand more about connectionstring or create one, use the following site for template: http://www.connectionstrings.com/sql-server/
You can get the necessary database details by viewing the Properties of your database via "SQL Server Management Studio" (right click and select Properties --> View Connection Properties)

I met the same question. The key step is here.
I used vs 2013 update 4.
When you configured your SQL in azure, it generated a connect string.

Is there a universal connection string for different computers to connect to a local database using my program developed by vs2010

newbie here.
I have a local db in my program. Whilst I was developing the program I used the SQL
Connection string :
SqlConnection sconn = new SqlConnection(#"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\leemk_000\Documents\......Integrated Security=True;User Instance=True;");
Now If I want to load this program onto a different computer I am sure that this connection will no longer work simply because it will still be looking for Users\Lee_000\
I have tried to remove Lee_000 but I get this following error:
An attempt to attach an auto-named database for file C:\Users\Documents..... failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.
What can I do to get a connection string to work on different computers.
With many thanks

The whole User Instance and AttachDbFileName= approach is flawed - at best - especially when you want to share your database amongst multiple clients!
When running your app in Visual Studio, it will be copying around the .mdf file (from your App_Data directory to the output directory - typically .\bin\debug - where you app runs) and most likely, your INSERT works just fine - but you're just looking at the wrong .mdf file in the end!
If you want to stick with this approach, then try putting a breakpoint on the myConnection.Close() call - and then inspect the .mdf file with SQL Server Mgmt Studio Express - I'm almost certain your data is there.
The real solution in my opinion would be to
install SQL Server Express (and you've already done that anyway)
install SQL Server Management Studio Express
create your database in SSMS Express, give it a logical name (e.g. YourDatabase)
connect to it using its logical database name (given when you create it on the server) - and don't mess around with physical database files and user instances. In that case, your connection string would be something like:
Data Source=.\\SQLEXPRESS;Database=YourDatabase;Integrated Security=True
and everything else is exactly the same as before...

If it's a local db you should be placing it within the app folder and carry it with the app right?
Put the database in the App_data folder of your app and use that in your connection string
<add name="YourConnectionString" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\yourfile.mdf;Integrated Security=True;User Instance=True" providerName="System.Data.SqlClient"/>

You need to use a database server and let your users use it via your connection string like this;
Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;
"myServerAddress" should be the ip adress of your server machine.

Connection string for remote SQL server 2008 without SQL Management Studio

I know its a classic problem, but I am too novice to even comprehend the basics (sorry). I have this ASP.NET "Website" with databases (SQL Server 2008), which I am trying to deploy on a Remote Host Server (HostGator) using WebSite Copy tool of VS 2010.
In VS 2010, I could grab the Connection string directly through the "property" of the database, which turned out to be:
Data
Source=.\SQLEXPRESS;AttachDbFilename="C:\Users\myName\Documents\Visual
Studio 2010\WebSites\Experiment\App_Data\data.mdf";Integrated
Security=True;User Instance=True
Now, I know that a website called http://connectionstrings.com/ exists, but its too overwhelming for me at first glance.
My current connection string:
Data
Source=domainName.com\SQLEXPRESS;AttachDbFilename=C:\inetpub\vhosts\domainName\httpdocs\Experiment\App_Data\data.mdf;Integrated
Security=True;User Instance=True
I am pretty sure, that this is wrong as its giving me the classic error of:
A network-related or instance-specific error occurred while
establishing a connection to SQL Server..
But I don't know how to fix it. Where to start looking, how to initiate, how to get the parameters required to build the connection string. How to find the path of the AttachDbFilename ? Can you please help?
I believe, that connection string is the only parameter which needs to be modified. If there's something else, then please suggest? Also, I keep coming across the usage of SQL Management Studio to make things work, I don't have that, so is it hard to accomplish this without it?
Please help, thanks.

You can't specify a directory relative to your own machine.
Change AttachDbFilename to
AttachDbFilename=|DataDirectory|data.mdf
The specifics for Data Source should be given to you from your hosting company, as well the security model (probably you need to use a specific user)
You can download SqlServer Management Studio Express from this link

Man,
What do you think about HttpServerUtility.MapPath Method. It returns the physical file path that corresponds to the specified virtual path on the Web server.
[]'s

When you get your hosting. They will provide the connection string for you. like this
<add name="ConnectionStringName"
connectionString="Data Source=localhost;Database=YourDatabaseName;Uid=YourUserNameForDatabase;password=yourpassword;"
providerName="System.Data.SqlClient" />
Let me know, if you need more help

Database Error while launching application

I deployed C# application and created installer. Installer gets created successfully but when tried to launch the application it throws up following error:
An attempt to attach an auto-named database for file CampusPointe.mdf
failed. A database with the same name exists, or specified file cannot
be opened, or it is located on UNC share.
connection string in app.config is as follows:
<connectionStrings>
<add name="App_Key_Management.Properties.Settings.VendorKeyConnectionString1"
connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename="C:\Program Files\Vendor Key Management\VendorKey.mdf";Integrated Security=True;Connect Timeout=30;User Instance=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
Any help would be appreciated.
Regards,
Sri

Sri,
First of all, you need to ensure a couple of things:
1. You have installed SQL Server
2. You need to deal with the creation or replacement of the file you created. I think this is your issue ... If the .mdf file exists then you need to either update the existing file or drop and replace it (USE [database] GO DROP TABLE... GO CRATE TABLE ... GO). You will also need to consider step 4 below.
3. If you are accessing a a file located in a database you need a fully formed name. You also need to add the database user to the connection string in ASP.NET Web.Config or App.config (depending on the app). I looks like you have started this ...
4. Make sure the user account that you are using in the connection string has the necessary privileges on the database side. If this is a full fledged database in SQL SERVER then the user account will need update, delete, create privileges. If you are replacing or creating databases on the fly then the user will need CREATE DATABASE or DROP / CREATE privileges.
I think to best answer your question we would need more information on the architecture of the application. My guess is that your code creates the database fine the first time and then when you try to run it the second time it fails because the database is already there. If this is the case you also need to address your code (with IF statements or SWITCH CASE ... your call) to handle situations where the table (1) does not exist and needs to be created; (2) exists and needs to be updated; and / or (3) exists and needs to be replaced. The correct answer again depends on your code and what you are trying to do.