I'm an newbie who is trying to get learn some web programming. I'm making my site in VS 2012 using C#. I've got a database connected in the App_Data folder, using SQL Server CE 4.0. I'm attempting to connect to it as follows:
SqlCeCommand cmd1 = new SqlCeCommand("SELECT Admin FROM SystemUsers WHERE Email=" + user.Email);
SqlCeDataReader admin = null;
SqlCeConnection conn = new SqlCeConnection();
conn.ConnectionString = "Data Source=MyData.sdf;Persist Security Info=False;";
conn.Open();
admin = cmd1.ExecuteReader();
When I execute this, I get the following error:
An exception of type 'System.Data.SqlServerCe.SqlCeException' occurred in System.Data.SqlServerCe.dll but was not handled in user code
Any thoughts as to what I'm doing wrong? I've been trying to figure this out for hours.
You said that your database is in the APP_Data directory, but your connection string assumes that is in the root directory of your site.
Try with
conn.ConnectionString = #"Data Source|DataDirectory|\MyData.sdf;Persist Security Info=False;";
The |DataDirectory| is a placeholder string that the NET Framework changes to a predefined location where you data files are supposed to stay
And this is how I would change your code
using(SqlCeConnection conn = new SqlCeConnection(#"Data Source|DataDirectory|\MyData.sdf;Persist Security Info=False;"))
using(SqlCeCommand cmd1 = new SqlCeCommand("SELECT Admin FROM SystemUsers WHERE Email=#mail", conn))
{
conn.Open();
cmd1.Parameters.AddWithValue("#mail", user.Email);
SqlCeDataReader admin = cmd1.ExecuteReader();
while(admin.Read())
{
.....
}
}
As you can see, I have made this changes:
Added a using statement around the creation of the connection and of
the command. This will ensure proper closing and disposing of the two
objects.
Added a parameterized query to avoid problems in parsing text strings
and Sql Injections
Related
I have two computers. One is running SQL Server, and I can access the server using SQL authentication from the 2nd PC using SSMS.
I have created a C# Windows Forms application that connects to the database. However, I couldn't access my server from the application.
I disabled the firewall, allowed remote control, and allowed mixed mode authentication. I also forwarded required ports to my IP in my router settings.
I tried both these connecting strings, but they didn't help:
"Persist Security Info = False; User ID = gues; Password=gues;Initial Catalog = CoronaNurse; Server=" + server;
"Data Source=" + server + ";Initial Catalog=CoronaNurse;Integrated Security=false;UID=gues;Password=gues";
(server is a string that have IP of my server)
(gues is a login in my Server)
The weird thing is when I login as gues in SSMS from my 2nd computer I can access the server in the first computer.
The question is, how do I access my server from a computer that doesn't have SSMS or any specific Login?
I need my application to be able to connect to my server without anything else installed, but I can't find where my problem is.
Adding from comments:
Im using the connecting to get a con string from my DB depends on the table i get with my gue.login function SqlDataAdapter
adapter = new SqlDataAdapter("select * from gue.login('" + textBox1.Text.Trim() + "', '" + textBox2.Text.Trim() + "', '" + server + "')", conn);
SqlCommandBuilder cb = new SqlCommandBuilder(adapter);
DataSet ds = new DataSet();
adapter.Fill(ds);
string connection;
connection = ds.Tables[0].Rows[0][0].ToString();
Unless you haven't posted up all of your code, you don't appear to be controlling your SQL connection and I would strongly suggest that you use a parameterised call to protect against SQL injection from using direct text entry field values e.g.:
var dataset = new DataSet();
using (var connection = new SqlConnection(SqlConnectionString))
{
connection.Open();
var command = new SqlCommand("GetAll", connection);
command.CommandType = CommandType.StoredProcedure;
var adapter = new SqlDataAdapter(command);
adapter.Fill(dataset);
...
}
The SQL is wrong, and the connection strings look a little off. You might also need an instance name as part of the server. For example, instead of just localhost or 192.168.0.20, you might need localhost\SQLExpress or 192.168.0.20\..
One way you can find the connection string for sure is to use Visual Studio instead of SSMS to connect to the database. The Visual Studio Database Tools has a similar connection window as SSMS, and you can use it to show you the actual connection string it used.
When you've figured that out, try something more like this:
var connString = $"Server={server};Database=CoronaNurse;User Id=gues;Password=gues";
var sql = "select * from gue.login WHERE username = #username AND pHash = #pHash";
var ds = new DataSet();
using (var conn = new SqlConnection(connString))
using (var cmd = new SqlCommand(sql, conn))
using (var adapter = new SqlDataAdapter(cmd))
{
cmd.Parameters.Add("#username", SqlDbType.NVarChar, 50).Value = textBox1.Text.Trim();
cmd.Parameters.Add("#pHash", SqlDbType.Char, 60).Value = BCrypt.Net.BCrypt.HashPassword(textBox2.Text.Trim());
adapter.Fill(ds);
var connection = ds.Tables[0].Rows[0].Items[0].ToString();
}
Note the use of both parameterized queries and BCrypt (you can add BCrypt via NuGet). There are a few things in database development that are too important to do wrong, even for proof-of-concept and learning projects. One of these is SQL Injection. Another is password handling. What I posted still isn't quite right for password handling (you should instead retrieve the stored hash and use the Verify() method), but it's close enough to set you on the right path.
Someone has told me that I can't access my online SQL Server DB from a client PC that doesn't have a Local DB.
I guess that explains my problem perfectly!
I never knew that, in my case, that is my problem right?
I have a legacy Visual FoxPro database from which I need to get the data from.
I have DBC, DCT, DCX & FPT files in the database folder.
I installed the Visual FoxPro provider & driver and wrote a short C# program to access the data.
I also made sure the program is running in 32bit mode, since I understood that the VFP driver is 32bit.
However I'm getting the following error:
Additional information: Connectivity error: [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
I made sure that the driver name ("Microsoft Visual FoxPro Driver") as appears in the Windows ODBC 32bit administration tool is specified in the connection string, but it doesn't seem to help.
The code:
OleDbConnection yourConnectionHandler = new OleDbConnection(
#"Provider=VFPOLEDB.1;DRIVER=Microsoft Visual FoxPro Driver;Data Source=mydatabase.dbc;Mode=Read;Collating Sequence=machine");
// Open the connection, and if open successfully, you can try to query it
yourConnectionHandler.Open();
if (yourConnectionHandler.State == ConnectionState.Open)
{
string mySQL = "select * from tablename";
var command = yourConnectionHandler.CreateCommand();
command.CommandText = mySQL;
var res = command.ExecuteReader(); // throws the error
yourConnectionHandler.Close();
}
I've been stuck on this for a long time, and have tried everything I could find on the net.
Any idea?
You are saying provider and trying to use OleDbConnection (which is right) but defining an ODBC driver within the connection string. In other words, your connection string is wrong.
using (OleDbConnection cn = new OleDbConnection(
#"Provider=VFPOLEDB;Data Source=c:\MyPath\mydatabase.dbc;Mode=Read;Collating Sequence=machine"))
using (OleDbCommand cmd = new OleDbCommand("select * from tablename", cn))
{
cn.Open();
var reader = cmd.ExecuteReader();
// do something with the reader. ie:
// someDataTable.Load(reader);
cn.Close();
}
It works wonderfully well. In connectionstring you don't need to use the database name, you can just use the tables' path as the data source.
I'm trying to open a connection to a DB and then insert a record into a table. At the moment it's just a simple localDB, I have looked at opening the connection with the sqlclient namespace methods.
SqlConnection con = new SqlConnection("Data Source=(LocalDB)\\MSSQLLocalDB;
AttachDbFilename=C:\\FILE\\PATH\\EXAMPLE\\TechMVCDB.mdf;Integrated Security=True;
Connect Timeout=30");
I'm not certain that my connection string is even correct, I got it directly from the connection string box when you click on your database in the server explorer panel. I added a breakpoint in the code after the connection was opened and a select all statement was executed :
SqlConnection con = new SqlConnection("Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=C:\\FILE\\PATH\\EXAMPLE\\TechMVCDB.mdf;Integrated Security=True;Connect Timeout=30");
con.Open();
SqlCommand com = new SqlCommand();
com.Connection = con;
com.CommandText = "SELECT * FROM Table ORDER BY Id";
SqlDataReader rdr = com.ExecuteReader();
I then get this error "System.Data.SqlClient.SqlException: 'Incorrect syntax near the keyword 'Table'.'" Table was just simply the name of the table was it also treating it as a keyword?
After this I changed the tablename to TechTester and ran it again, it ran with no errors and seemed to get the correct field amount of 4 id,sequence,direction,time it didn't seem to get the inserted test data.
I've also looked at using the Entity framework and implemented the very beginnings of it so I have my entity model class setup but nothing more. Is this the direction I should actually go with? How would I access the entity database?
My question is How do I best open a connection to a local db in asp.net-MVC using C#?
Table is one of the SQL Server reserved keywords.
I googled for half a day how to set the path of my database so if I put it on an other computer it will work. I would keep googling but I really need the answer really fast... I'll have to use it to a competition in few hours.
string path = Path.Combine(Application.StartupPath, "Database1.mdf");
SqlConnection conn = new SqlConnection(#"Data Source=(LocalDB)\v11.0;AttachDbFilename=" + path + ";");
conn.Open();
SqlCommand command = new SqlCommand("SELECT NAME FROM DATA", conn);
SqlDataReader reader = command.ExecuteReader();
while(reader.Read())
{
string text = reader.GetString(0);
MessageBox.Show(text);
}
SqlCommand c = new SqlCommand("INSERT INTO DATA (id, name) VALUES(i, v)", conn);
c.Parameters.AddWithValue("#i", 1);
c.Parameters.AddWithValue("#v", "Jack");
c.ExecuteNonQuery();
conn.Dispose();
This code is working for selection but not for insertion. Then I hardcoded the path into:
String s = #"C:\Users\Radu\Documents\Visual Studio 2013\Projects\WindowsFormsApplication7\WindowsFormsApplication7\Database1.mdf";
and it works for both so it's not the SQL statement that is wrong.
So my question is: what is the path I should put into my SqlConnection object so that when they get my source code on my competition and test it on another pc it will work.
LocalDB is meant exclusively for development. You cannot use it in production. In your case, 'production' means the competition. Unless the competition organizer specifies that they support a SQL Server instance for you to connect to, and give out the connection parameters (ie. very unlikely), you shouldn't use use SQL Server in your project.
You can put the MDF file on any file share that your computer has access to. Just alter the path variable to point at the correct file share.
See answers to your question here Can SQL Server Express LocalDB be connected to remotely?
Suppose I have created a SQL Server database called Database1.mdf in the App_Data folder in Visual Studio with a table called Names.
How could I establish a connection to read the table values using C#?
So far I've tried something like this:
SqlConnection conn = new SqlConnection("Server=localhost;Database=Database1;");
conn.Open();
// create a SqlCommand object for this connection
SqlCommand command = conn.CreateCommand();
command.CommandText = "Select * from Names";
But I get an error:
database not found/error connecting to database
In Data Source (on the left of Visual Studio) right click on the database, then Configure Data Source With Wizard. A new window will appear, expand the Connection string, you can find the connection string in there
If you use SQL authentication, use this:
using System.Data.SqlClient;
SqlConnection conn = new SqlConnection();
conn.ConnectionString =
"Data Source=.\SQLExpress;" +
"User Instance=true;" +
"User Id=UserName;" +
"Password=Secret;" +
"AttachDbFilename=|DataDirectory|Database1.mdf;"
conn.Open();
If you use Windows authentication, use this:
using System.Data.SqlClient;
SqlConnection conn = new SqlConnection();
conn.ConnectionString =
"Data Source=.\SQLExpress;" +
"User Instance=true;" +
"Integrated Security=true;" +
"AttachDbFilename=|DataDirectory|Database1.mdf;"
conn.Open();
If you're using SQL Server express, change
SqlConnection conn = new SqlConnection("Server=localhost;"
+ "Database=Database1;");
to
SqlConnection conn = new SqlConnection("Server=localhost\SQLExpress;"
+ "Database=Database1;");
That, and hundreds more connection strings can be found at http://www.connectionstrings.com/
SqlConnection c = new SqlConnection(#"Data Source=localhost;
Initial Catalog=Northwind; Integrated Security=True");
You try with this string connection
Server=.\SQLExpress;AttachDbFilename=|DataDirectory|Database1.mdf;Database=dbname; Trusted_Connection=Yes;
I like to use the handy process outlined here to build connection strings using a .udl file. This allows you to test them from within the udl file to ensure that you can connect before you run any code.
Hope that helps.
Visual Studio 2019 (and probably a few previous versions).
View -> SQL Server Object Explorer
Top of the tree is 'SQL Server'
Under 'SQL Server', are couple of '(localdb)....'
Expand the (localdb)... -> Databases until you find your db.
Database Name (eg. Database1) -> Right-click -> Properties, and scroll the many properties (eg. "ANSI
NULL Default"). Find the "Connection string" property, copy the value
into your code, and you're running.