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Interacting with SQL Server database in Visual Studio 2015

I realise this question could be quite broad but ive been searching for the past 2 days with no luck.
I've created a project in Visual Studio 2015 and created a new data source in that project using a cloud database created with SQL Server Management Studio.
I'm now trying to code a login page in the project, which gets a username and password from 2 textboxes on the UI and executes an SQL query to check if the user exists in the database and if their password is right.
I'm familiar with Java code for database connections, such as the prepared statement and resultset functions.
Is there something equivalent for C#?
Thank you, reference to helpful articles or code samples will be greatly appreciated.

I think this can help you :-
http://csharp.net-informations.com/data-providers/csharp-sql-server-connection.htm
http://www.codeproject.com/Articles/823854/How-to-connect-SQL-Database-to-your-Csharp-program

here is probably the fastest but not the best way to check it.
string yourConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Users.accdb; Persist Security";
using (OleDbConnection conn = new OleDbConnection(yourConnectionString))
{
try
{
conn.Open();
using (OleDbCommand cmd = new OleDbCommand("Select * from UsersTable where UName = #Username and Pass = #Password"))
{
cmd.Parameters.AddWithValue("#Username", txtUserName.Text);
cmd.Parameters.AddWithValue("#Password", txtPass.Text);
using (OleDbDataReader r = cmd.ExecuteReader())
{
if (r.HasRows)
{
Console.WriteLine("User exists")
}
else
{
Console.WriteLine("User does not exist")
}
}
}
}
catch (Exception exc)
{
MessageBox.Show(exc.Message);
}
}

Error when using insert in access: Could not Update; currently locked

I have a WebService that updates my access table from some terminals (10).
When I try to update I get this error from the error log:
Could not Update; Currently locked
Some terminals succeed and some do not.
I update like this:
using (Conn = new OleDbConnection(Work_Connect))
{
Conn.Open();
foreach (DataRow R in ds.Tables["MyCount"].Rows)
{
U_ID = ID;
U_Bar = R["Bar"].ToString().Trim();
U_Qty = R["Qty"].ToString().Trim();
U_Des = R["Des"].ToString().Trim();
SQL = "INSERT INTO MyTbl(ID,Bar,Qty,Des)VALUES('";
SQL += Convert.ToInt32(ID) + "','" + U_Bar + "','" + Convert.ToDouble(U_Qty) + "','" + U_Des + "')";
OleDbCommand Cmd2 = new OleDbCommand(SQL, Conn);
Cmd2.CommandText = SQL;
Cmd2.ExecuteNonQuery();
}
}
GC.Collect();
return true;

MsAccess has serious drawbacks for multi-user update. The Jet engine is not a database server, and will manage concurrence based on file system locking. If your problem is with a web service, I'd move the update to the server part, and implement queuing of simultaneous requests there. Thus, only the server, one process, will have access to the Access data. The other option is to use a real database server that will do that work for you. SQL Server Express is the usual option because it's easy to integrate, it's free as in beer, and is solid.
Also, if your problem happens always from the same terminals, that is, some terminals can never update anything, check the file access rights of these terminals' users to the database file, the lock file, and the database and lock file directory. Write rights are required for all of them.

Suggestions:
Convert your query to a parameterized query to avoid any potential strangeness with quoting. (You are converting text to numbers and then enclosing them in single-quotes in the SQL statement. That makes no sense.)
Don't force garbage collection on each call. According to the MSDN article here: "It is possible to force garbage collection by calling Collect, but most of the time, this should be avoided because it may create performance issues."
Try something like this instead:
using (Conn = new OleDbConnection(Work_Connect))
{
Conn.Open();
foreach (DataRow R in ds.Tables["MyCount"].Rows)
{
U_ID = ID;
U_Bar = R["Bar"].ToString().Trim();
U_Qty = R["Qty"].ToString().Trim();
U_Des = R["Des"].ToString().Trim();
SQL = "INSERT INTO MyTbl (ID,Bar,Qty,Des) VALUES (?,?,?,?)";
using(OleDbCommand Cmd2 = new OleDbCommand(SQL, Conn))
{
// Cmd2.CommandText = SQL; redundant, the 'new' set the .CommandText
Cmd2.Parameters.AddWithValue("?", Convert.ToInt32(ID));
Cmd2.Parameters.AddWithValue("?", U_Bar);
Cmd2.Parameters.AddWithValue("?", Convert.ToDouble(U_Qty));
Cmd2.Parameters.AddWithValue("?", U_Des);
Cmd2.ExecuteNonQuery();
}
}
Conn.Close();
}
// GC.Collect(); // disabled for test purposes
return true;

How to add/edit/retrieve data using Local Database file in Microsoft Visual Studio 2012

I want to get into developing applications that use databases. I am fairly experienced (as an amateur) at web based database utilization (mysql, pdo, mssql with php and old style asp) so my SQL knowledge is fairly good.
Things I have done already..
Create forms application
Add four text boxes (first name, last name, email, phone)
Added a datagrid control
Created a database connection using 'Microsoft SQL Server Database File (SqlClient)'
Created a table with fields corresponding to the four text boxes.
What I want to be able to do now is, when a button is clicked, the contents of the four edit boxes are inserted using SQL. I don't want to use any 'wrapper' code that hides the SQL from me. I want to use my experience with SQL as much as possible.
So I guess what I am asking is how do I now write the necessary code to run an SQL query to insert that data. I don't need to know the SQL code obviously, just the c# code to use the 'local database file' connection to run the SQL query.
An aside question might be - is there a better/simpler way of doing this than using the 'Microsoft SQL Server Database File' connection type (I have used it because it looks like it's a way to do it without having to set up an entire sql server)

The below is inserting data using parameters which I believe is a better approach:
var insertSQL = "INSERT INTO yourTable (firstName, lastName, email, phone) VALUES (firstName, lastName, email, phone)";
string connectionString = "Data Source=myServerAddress;Initial Catalog=myDataBase;Integrated Security=SSPI; User ID=userid;Password=pwd;"
using (var cn = new SqlCeConnection(connectionString))
using (var cmd = new SqlCeCommand(insertSQL, cn))
{
cn.Open();
cmd.Parameters.Add("firstName", SqlDbType.NVarChar);
cmd.Parameters.Add("lastName", SqlDbType.NVarChar);
cmd.Parameters.Add("email", SqlDbType.NVarChar);
cmd.Parameters.Add("phone", SqlDbType.NVarChar);
cmd.Parameters["firstName"].Value = firstName;
cmd.Parameters["lastName"].Value = lastName;
cmd.Parameters["email"].Value = email;
cmd.Parameters["phone"].Value = phone;
cmd.ExecuteNonQuery();
}
This is selecting data from database and populating datagridview:
var dt = new DataTable();
string connectionString = "Data Source=myServerAddress;Initial Catalog=myDataBase;Integrated Security=SSPI; User ID=userid;Password=pwd;"
using (var cn = new SqlCeConnection(connectionString )
using (var cmd = new SqlCeCommand("Select * From yourTable", cn))
{
cn.Open();
using (var reader = cmd.ExecuteReader())
{
dt.Load(reader);
//resize the DataGridView columns to fit the newly loaded content.
yourDataGridView.AutoSize = true; yourDataGridView.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCells);
//bind the data to the grid
yourDataGridView.DataSource = dt;
}
}

This first example is an over view based upon how I think it will be easier to understand but this is not a recommended approach due to vulnerability to SQL injection (a better approach further down). However, I feel it is easier to understand.
private void InsertToSql(string wordToInsert)
{
string connectionString = Data Source=myServerAddress;Initial Catalog=myDataBase;Integrated Security=SSPI; User ID=myDomain\myUsername;Password=myPassword;
string queryString = "INSERT INTO table_name (column1) VALUES (" + wordToInsert + ")"; //update as you feel fit of course for insert/update etc
using (SqlConnection connection = new SqlConnection(connectionString))
{
connection.Open()
SqlDataAdapter adapter = new SqlDataAdapter();
SqlCommand command = new SqlCommand(queryString, connection);
command.ExecuteNonQuery();
connection.Close();
}
}
I would also suggest wrapping it in a try/catch block to ensure the connection closes if it errors.
I am not able to test this but I think it is OK!
Again don't do the above in live as it allows SQL injection - use parameters instead. However, it may be argued it is easier to do the above if you come from PHP background (just to get comfortable).
This uses parameters:
public void Insert(string customerName)
{
try
{
string connectionString = Data Source=myServerAddress;Initial Catalog=myDataBase;Integrated Security=SSPI; User ID=myDomain\myUsername;Password=myPassword;
using (SqlConnection connection = new SqlConnection(connectionString))
{
connection.Open();
connection.Open() SqlCommand command = new SqlCommand( "INSERT INTO Customers (CustomerName" + "VALUES (#Name)", connection);
command.Parameters.Add("#Name", SqlDbType.NChar, 50, " + customerName +");
command.ExecuteNonQuery();
connection.Close();
}
catch()
{
//Logic in here
}
finally()
{
if(con.State == ConnectionState.Open)
{
connection.Close();
}
}
}
And then you just change the SQL string to select or add!

When using an OracleCommand in .net must the OracleClient be installed on the machine or does .net cover this?

I want to make a simple query on an Oracle database from .net using similar code to this.
using System;
using System.Data;
using Oracle.DataAccess.Client;
class Sample
{
static void Main()
{
// Connect to Oracle
string constr = "User Id=scott;Password=tiger;Data Source=AKI1.WORLD";
OracleConnection con = new OracleConnection(constr);
con.Open();
// Display Version Number
Console.WriteLine("Connected to Oracle " + con.ServerVersion);
// Read REF CURSOR into DataSet
DataSet ds = new DataSet();
OracleCommand cmd = con.CreateCommand();
cmd.CommandText = "GetComplexTabPkg.GetEmp";
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("p_dep", OracleDbType.Int16).Value = 20;
cmd.Parameters.Add("p_ref", OracleDbType.RefCursor).Direction
= ParameterDirection.Output;
OracleDataAdapter da = new OracleDataAdapter(cmd);
da.TableMappings.Add("Emp", "Emp");
da.Fill(ds);
// Close and Dispose OracleConnection
con.Close();
con.Dispose();
// Show Message
Console.WriteLine("DataSet filled");
}
}
My only concern is does the Oracle Client need to be installed on the web server that is running this code? It's my first time using this and I would like to avoid any obvious issues that can be prevented. Thanks.

Yes, Oracle Client need to be installed in web server. The work around will be to ship your application with Instant Oracle Client

On my Own I just install 64-bit Oracle Data Access Components (ODAC) Downloads, which seems to be lighter than Oracle Client.

Multiple "Insert Into" operation under same event

Guys I searched around like hell but nothing could help me so I think it's time to ask. Before I write to problem, I need to say that I need it's solution asap because it's a project that I have to give tomorrow and I stuck on the same subject since ages and still losing time.
OK here it is;
I need to add a book to a library system, at first phase I add the standard book features which has only "one value" like (name, page number, publishing time, publisherID etc) but as wanted by me book MAY HAVE MULTIPLE WRITERS AND CATEGORIES which killed me and still I can't resolve. I tried to add book to it's (books) table then with the information i got from that i did an other insert op. to (bookWriters) table. While I check it, compiler does everything in order without error but when I check table from SQL Server there is nothing.
Here is what I tried to do;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Data.SqlClient;
namespace Project_
{
public partial class addBook: Form
{
public addBook()
{
InitializeComponent();
}
public main refForm;
int chosenWritersNumber; //how many writers have selected on listbox
int[] writers= { }; // an array list that i keep writerIDs that comes from class
int ind = 0;
int insertedBookID; // to catch latest added book's ID
int chosenWriterID; // writer that will be added
private void bookAddingPreps()
{
chosenWritersNumber = lstWriters.SelectedItems.Count;
Array.Resize<int>(ref writers, chosenWritersNumber );
for (int i = 0; i < chosenWritersNumber ; i++)
{
writers[i] = ((X_Writers)lstWriters.SelectedItems[i]).XWriterID;
}
}
private void addMainBookInfos()
{
SqlConnection con = new SqlConnection(Conn.Activated);
SqlCommand com = new SqlCommand("AddBook", con);
com.CommandType = CommandType.StoredProcedure;
com.Parameters.AddWithValue("#BookISBN", txtISBN.Text);
con.Close();
}
private void catchAddedBookID()
{
SqlConnection con = new SqlConnection(Conn.Activated);
SqlCommand com = new SqlCommand("catchBookID", con);
com.CommandType = CommandType.StoredProcedure;
con.Open();
SqlDataReader dr = com.ExecuteReader();
if (dr.HasRows)
{
while (dr.Read())
{
insertedBookID = dr.GetInt32(0);
}
}
dr.Close();
con.Close();
}
private void addWritersOfTheBook()
{
chosenWriterID = writers[ind];
SqlConnection con = new SqlConnection(Conn.Activated);
SqlCommand com = new SqlCommand("addBookWriters", con);
com.CommandType = CommandType.StoredProcedure;
com.Parameters.AddWithValue("#BookID", insertedBookID);
com.Parameters.AddWithValue("#WriterID", chosenWriterID);
con.Close();
}
I call these methods on click of a button. You see also stored procedure names but as I checked they all correct, there must be a mistake in this page that I still cant see but if it's needed I can add what procedures writes but they all tested and seems working.
So as i said, when i do this, as ind = 0, a writer should have been added, break point shows everything is ok and compiler doesnt show any errors but when I check sql server table, its empty.
Written in C# with using Visual Studio 2010 Ultimate and SQL Server 2008 Dev.
Thanks

You forget to execute your SqlCommand's. Make a call to command.ExecuteNonReader(); to execute it without expecting any results. see: http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.aspx
Apart form that, dont forget to dispose the resources acquired in your methods. Something like:
private void addMainBookInfos()
{
using (SqlConnection con = new SqlConnection(Conn.Activated))
using (SqlCommand com = new SqlCommand("AddBook", con))
{
com.CommandType = CommandType.StoredProcedure;
com.Parameters.AddWithValue("#BookISBN", txtISBN.Text);
com.ExecuteNonQuery()
// close can be omitted since you are already using the 'using' statement which automatically closes the connection
con.Close();
}
}