I have to connect my web application(C#, .NET) with database (SQL server 2005)

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i am using below code but i am using windows authentication. visual studio is showing below error.

"A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)"

Please let me know how to use windows authentication for database connection.

What I have tried:

protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection("server=hp-pc;database=admin.mdf");
con.Open();
string q = "insert into (user_id,name,password,email_id,contact,user_type) values('" + TextBox1.Text + "','" + TextBox2.Text + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "')";
SqlCommand com = new SqlCommand(q, con);
com.ExecuteNonQuery();
Response.Write("alert('saved')");
Response.Redirect("index.aspx");

Posted 27-Jan-17 1:56am

Member 12950401

Updated 27-Jan-17 7:54am

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[no name] 27-Jan-17 8:07am

"windows authentication for database connection", you add your username and password to your connection string. Why you think that will fix your error is anyone's guess. And, you might want to research SQL injection attacks. You have a pretty nice opening for one going on there.

Member 12950401 27-Jan-17 8:53am

Thank you

Jochen Arndt 27-Jan-17 8:14am

See https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring(v=vs.110).aspx
for the SQL connection string syntax.

Richard Deeming 27-Jan-17 9:33am

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

Richard Deeming 27-Jan-17 9:33am

Also, you're storing passwords in plain-text. You should only ever store a salted hash of the user's password, using a unique salt per record.

Secure Password Authentication Explained Simply[^]
Salted Password Hashing - Doing it Right[^]

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ZurdoDev · Answer 1 · 2017-01-27T07:54:00

If you want to use windows authentication then you need to change the identity on your application pool in IIS to run using a windows account that has access to sql. The identity on the Application Pool is the account your ASP.Net code will run as.

However, you probably and usually want to use a sql account instead and place your connection string in the web.config.

Also, do the other things mentioned in the comments so you have good safe code.