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ConnectionString ASP.NET

SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["SqlDataSource1"].ToString());
<connectionStrings>
<add name="SqlDataSource1"
connectionString="Data Source=(LocalDb)\MSSQLLocalDB;Initial Catalog=SqlDataSource3;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\SqlDataSource3.mdf"
providerName="System.Data.SqlClient"/>
</connectionStrings>
Should that work now?
Is at ConnectionStrings["XXX"] has to be placed Name or Initial Catalog of connectionStrings?

As shown on this page, the index value is the name of the connection string. Therefore your code is correct.
Now wondering why you have posted the question. Does your code not work?

Try this:
<add name="SqlDataSource1" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;Initial Catalog=SqlDataSource3;Integrated Security=True"/>
and then:
SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["SqlDataSource1"].ConnectionString);
Hope this helps.

Connection string has quotation mark, how to pass it to SqlConnection

I have created a LocalDB database in my project and its connection string is :
Data Source=(LocalDB)\v11.0;AttachDbFilename="E:\Projects\visual studio 2013\Projects\sqlce\mydb.mdf";Integrated Security=True;Connect Timeout=30
How should I pass it to SqlConnection()?
Note that it has an address within quotation marks. Have I done anything wrong?
I guess even if I program it correctly it won't work in another computer which doesn't have that .mdf file in that exact place. Isn't it so?
How can I have a program with a portable database so I can easily publish my pp?

Add the mdf file to your solution and and change the property "Copy to Output Directory" to Copy Always. Don't hardcode the mdf file path in connection string. Add the connection string in app.config or web.config file like below:
<connectionStrings>
<add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\myDB.mdf;Initial Catalog=MyDatabaseName;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
Then you can access the connection string in your C# code as below:
string conStr = System.Configuration.ConfigurationManager.ConnectionStrings["DefaultConnection"].ToString()
If you face any error regarding accessing the mdf file, the you can set the DataDirectory in your C# code using AppDomain.CurrentDomain.SetData() method.

<connectionStrings>
<add
name="NorthwindConnectionString"
connectionString="Data Source=serverName;Initial
Catalog=Northwind;Persist Security Info=True;User
ID=userName;Password=password"
providerName="System.Data.SqlClient"
/>
</connectionStrings>
you can access by
connString =rootWebConfig.ConnectionStrings.ConnectionStrings["NorthwindConnectionString"];
More about connection string
SqlConnection con = new SqlConnection(connstring);
or you can go in this way like
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString);

sql connection is making exception in asp.net

I have this code
SqlConnection sqlConnection = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["TestStoredProcedure"].ConnectionString);
This is my web.config
<add name="=TestStoredProcedure" connectionString="Data Source=.;Initial Catalog=testSqlServer;Integrated Security=True"/>
I got this exception:
Object reference not set to an instance of an object.
on the connection string line.

You're referencing ConnectionString on something that doesn't exist:
ConnectionStrings["TestStoredProcedure"].ConnectionString
Your config file has =TestStoredProcedure as the name. That doesn't match your code. Remove the =.

Include following namespace line in your header of the page.
using System.Configuration;
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["TestStoredProcedure"].ConnectionString);
Web.Confiq:
<connectionStrings>
<add name="TestStoredProcedure" connectionString="Data Source=.;Initial Catalog=testSqlServer;Integrated Security=True"/>
</connectionStrings>
Also remove '=' from the name of the connection string.

How to solve database initialization error?

I have been testing out different things and have concluded that the following error is the reason my database will not initialize and throws an exception. The exception occurs when I reference the database and initialize it. My Web.config connection string is fine as you can see. I am using Entity Framework 6, MSSQL, and C#. Any help would be appreciated.
Exception:
Cannot open database \"xxx\" requested by the login. The login failed.\r\nLogin failed for user 'xxxx'.
Connection String:
<add name="WebDBContext" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=WebDB;Integrated Security=SSPI;" providerName="System.Data.SqlClient"/>
Code:
private SchoolContext db = new SchoolContext();
public ViewMethod Method()
{
var students = from s in db.Students select s; //EXCEPTION IS THROWN HERE
}

You should mention userid and password in connection string
<add name="WebDBContext" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=WebDB;Integrated Security=SSPI;User ID=xyz;pwd=top$secret;" providerName="System.Data.SqlClient"/>

Your connection string is not in the format required by EF, it should actually look similiar to this:
<add name="XYZ" connectionString="metadata=res://*/ModEntity.csdl|res://*/ModEntity.ssdl|res://*/ModEntity.msl;provider=System.Data.SqlClient;provider connection string="Data Source=SomeServer;Initial Catalog=SomeCatalog;Persist Security Info=True;User ID=Entity;Password=SomePassword;MultipleActiveResultSets=True"" providerName="System.Data.EntityClient" />

Also use linq query.
var students = db.Students;
<connectionStrings>
<add name="WebDBContext" connectionString="metadata=res://*/Models.ModelName.csdl|res://*/Models.ModelName.ssdl|res://*/Models.ModelName.msl;provider=System.Data.SqlClient;provider connection string="data source=servername;initial catalog=databasename;user id=username;password=password;MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" />
</connectionStrings>
replace the ModelName to your Model and change connections on your db.

How to create a connection string in asp.net c#

I am working on asp.net c# project, for connection I used:
SqlConnection con = new SqlConnection(#"Data Source=.\SQLEXPRESS;AttachDbFilename=D:\19-02\ABCC\App_Data\abcc.mdf;Integrated Security=True;User Instance=True");
but I want to get this connection string to get configure and be like this, so can any one help how to create this kind of connection.
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["itmall"].ConnectionString);

Demo :
<connectionStrings>
<add name="myConnectionString" connectionString="server=localhost;database=myDb;uid=myUser;password=myPass;" />
</connectionStrings>
Based on your question:
<connectionStrings>
<add name="itmall" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=D:\19-02\ABCC\App_Data\abcc.mdf;Integrated Security=True;User Instance=True" />
</connectionStrings>
Refer links:
http://www.connectionstrings.com/store-connection-string-in-webconfig/
Retrive connection string from web.config file:
write the below code in your file where you want;
string connstring=ConfigurationManager.ConnectionStrings["itmall"].ConnectionString;
SqlConnection con = new SqlConnection(connstring);
or you can go in your way like
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["itmall"].ConnectionString);
Note:
The "name" which you gave in web.config file and name which you used in connection string must be same(like "itmall" in this solution.)

string connectionstring="DataSource=severname;InitialCatlog=databasename;Uid=; password=;"
SqlConnection con=new SqlConnection(connectionstring)

add this in web.config file
<configuration>
<appSettings>
<add key="ConnectionString" value="Your connection string which contains database id and password"/>
</appSettings>
</configuration>
.cs file
public ConnectionObjects()
{
string connectionstring= ConfigurationManager.AppSettings["ConnectionString"].ToString();
}
Hope this helps.

Add this in your web.config file
<connectionStrings>
<add name="itmall"
connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=D:\19-
02\ABCC\App_Data\abcc.mdf;Integrated Security=True;User Instance=True" />
</connectionStrings>

Add this connection string tag in web.config file:
<connectionStrings>
<add name="itmall"
connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=D:\19-02\ABCC\App_Data\abcc.mdf;Integrated Security=True;User Instance=True"/>
</connectionStrings>
And use it like you mentioned. :)

It occurs when IIS is not being connected to SQL SERVER. For a solution, see this screenshot: