I'm having an issue at the moment which I am trying to fix. I just tried to access a database and insert some values with the help of C#
The things I tried (worked)
String query = "INSERT INTO dbo.SMS_PW (id,username,password,email) VALUES ('abc', 'abc', 'abc', 'abc')";
A new line was inserted and everything worked fine, now I tried to insert a row using variables:
String query = "INSERT INTO dbo.SMS_PW (id,username,password,email) VALUES (#id, #username, #password, #email)";
command.Parameters.AddWithValue("#id","abc")
command.Parameters.AddWithValue("#username","abc")
command.Parameters.AddWithValue("#password","abc")
command.Parameters.AddWithValue("#email","abc")
command.ExecuteNonQuery();
Didn't work, no values were inserted. I tried one more thing
command.Parameters.AddWithValue("#id", SqlDbType.NChar);
command.Parameters["#id"].Value = "abc";
command.Parameters.AddWithValue("#username", SqlDbType.NChar);
command.Parameters["#username"].Value = "abc";
command.Parameters.AddWithValue("#password", SqlDbType.NChar);
command.Parameters["#password"].Value = "abc";
command.Parameters.AddWithValue("#email", SqlDbType.NChar);
command.Parameters["#email"].Value = "abc";
command.ExecuteNonQuery();
May anyone tell me what I am doing wrong?
Kind regards
EDIT:
in one other line I was creating a new SQL-Command
var cmd = new SqlCommand(query, connection);
Still not working and I can't find anything wrong in the code above.
I assume you have a connection to your database and you can not do the insert parameters using c #.
You are not adding the parameters in your query. It should look like:
String query = "INSERT INTO dbo.SMS_PW (id,username,password,email) VALUES (#id,#username,#password, #email)";
SqlCommand command = new SqlCommand(query, db.Connection);
command.Parameters.Add("#id","abc");
command.Parameters.Add("#username","abc");
command.Parameters.Add("#password","abc");
command.Parameters.Add("#email","abc");
command.ExecuteNonQuery();
Updated:
using(SqlConnection connection = new SqlConnection(_connectionString))
{
String query = "INSERT INTO dbo.SMS_PW (id,username,password,email) VALUES (#id,#username,#password, #email)";
using(SqlCommand command = new SqlCommand(query, connection))
{
command.Parameters.AddWithValue("#id", "abc");
command.Parameters.AddWithValue("#username", "abc");
command.Parameters.AddWithValue("#password", "abc");
command.Parameters.AddWithValue("#email", "abc");
connection.Open();
int result = command.ExecuteNonQuery();
// Check Error
if(result < 0)
Console.WriteLine("Error inserting data into Database!");
}
}
Try
String query = "INSERT INTO dbo.SMS_PW (id,username,password,email) VALUES (#id,#username, #password, #email)";
using(SqlConnection connection = new SqlConnection(connectionString))
using(SqlCommand command = new SqlCommand(query, connection))
{
//a shorter syntax to adding parameters
command.Parameters.Add("#id", SqlDbType.NChar).Value = "abc";
command.Parameters.Add("#username", SqlDbType.NChar).Value = "abc";
//a longer syntax for adding parameters
command.Parameters.Add("#password", SqlDbType.NChar).Value = "abc";
command.Parameters.Add("#email", SqlDbType.NChar).Value = "abc";
//make sure you open and close(after executing) the connection
connection.Open();
command.ExecuteNonQuery();
}
The most common mistake (especially when using express) to the "my insert didn't happen" is : looking in the wrong file.
If you are using file-based express (rather than strongly attached), then the file in your project folder (say, c:\dev\myproject\mydb.mbd) is not the file that is used in your program. When you build, that file is copied - for example to c:\dev\myproject\bin\debug\mydb.mbd; your program executes in the context of c:\dev\myproject\bin\debug\, and so it is here that you need to look to see if the edit actually happened. To check for sure: query for the data inside the application (after inserting it).
static SqlConnection myConnection;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
myConnection = new SqlConnection("server=localhost;" +
"Trusted_Connection=true;" +
"database=zxc; " +
"connection timeout=30");
try
{
myConnection.Open();
label1.Text = "connect successful";
}
catch (SqlException ex)
{
label1.Text = "connect fail";
MessageBox.Show(ex.Message);
}
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void button2_Click(object sender, EventArgs e)
{
String st = "INSERT INTO supplier(supplier_id, supplier_name)VALUES(" + textBox1.Text + ", " + textBox2.Text + ")";
SqlCommand sqlcom = new SqlCommand(st, myConnection);
try
{
sqlcom.ExecuteNonQuery();
MessageBox.Show("insert successful");
}
catch (SqlException ex)
{
MessageBox.Show(ex.Message);
}
}
private void button1_Click(object sender, EventArgs e)
{
String query = "INSERT INTO product (productid, productname,productdesc,productqty) VALUES (#txtitemid,#txtitemname,#txtitemdesc,#txtitemqty)";
try
{
using (SqlCommand command = new SqlCommand(query, con))
{
command.Parameters.AddWithValue("#txtitemid", txtitemid.Text);
command.Parameters.AddWithValue("#txtitemname", txtitemname.Text);
command.Parameters.AddWithValue("#txtitemdesc", txtitemdesc.Text);
command.Parameters.AddWithValue("#txtitemqty", txtitemqty.Text);
con.Open();
int result = command.ExecuteNonQuery();
// Check Error
if (result < 0)
MessageBox.Show("Error");
MessageBox.Show("Record...!", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
con.Close();
loader();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
con.Close();
}
}
public static string textDataSource = "Data Source=localhost;Initial
Catalog=TEST_C;User ID=sa;Password=P#ssw0rd";
public static bool ExtSql(string sql) {
SqlConnection cnn;
SqlCommand cmd;
cnn = new SqlConnection(textDataSource);
cmd = new SqlCommand(sql, cnn);
try {
cnn.Open();
cmd.ExecuteNonQuery();
cnn.Close();
return true;
}
catch (Exception) {
return false;
}
finally {
cmd.Dispose();
cnn = null;
cmd = null;
}
}
I have just wrote a reusable method for that, there is no answer here with reusable method so why not to share...here is the code from my current project:
public static int ParametersCommand(string query,List<SqlParameter> parameters)
{
SqlConnection connection = new SqlConnection(ConnectionString);
try
{
using (SqlCommand cmd = new SqlCommand(query, connection))
{ // for cases where no parameters needed
if (parameters != null)
{
cmd.Parameters.AddRange(parameters.ToArray());
}
connection.Open();
int result = cmd.ExecuteNonQuery();
return result;
}
}
catch (Exception ex)
{
AddEventToEventLogTable("ERROR in DAL.DataBase.ParametersCommand() method: " + ex.Message, 1);
return 0;
throw;
}
finally
{
CloseConnection(ref connection);
}
}
private static void CloseConnection(ref SqlConnection conn)
{
if (conn.State != ConnectionState.Closed)
{
conn.Close();
conn.Dispose();
}
}
class Program
{
static void Main(string[] args)
{
string connetionString = null;
SqlConnection connection;
SqlCommand command;
string sql = null;
connetionString = "Data Source=Server Name;Initial Catalog=DataBaseName;User ID=UserID;Password=Password";
sql = "INSERT INTO LoanRequest(idLoanRequest,RequestDate,Pickupdate,ReturnDate,EventDescription,LocationOfEvent,ApprovalComments,Quantity,Approved,EquipmentAvailable,ModifyRequest,Equipment,Requester)VALUES('5','2016-1-1','2016-2-2','2016-3-3','DescP','Loca1','Appcoment','2','true','true','true','4','5')";
connection = new SqlConnection(connetionString);
try
{
connection.Open();
Console.WriteLine(" Connection Opened ");
command = new SqlCommand(sql, connection);
SqlDataReader dr1 = command.ExecuteReader();
connection.Close();
}
catch (Exception ex)
{
Console.WriteLine("Can not open connection ! ");
}
}
}
Related
I created a folder on a webform in visual studio for images and titled as (Invoices), I want to save the root of images in MySql database and display the images on a panel one the webpage. The image has been saved on the folder but not on database.
The Codes I have tried
protected void Page_Load(object sender, EventArgs e)
{
string connection = "server=localhost; userid= ; password= ; database=admindb; allowuservariables=True";
MySqlConnection cn = new MySqlConnection(connection);
try
{
string sqlcmd = "SELECT PicAddress FROM InvoicesFP WHERE InvoicesFP_ID=#InvoicesFP_ID";
cn.Open();
MySqlCommand cmd = new MySqlCommand(sqlcmd, cn);
cmd.CommandType = CommandType.Text;
MySqlDataReader rdr = cmd.ExecuteReader();
while (rdr.Read())
{
string url = rdr["PicAddress"].ToString();
Image1.ImageUrl = url;
}
}
catch (Exception ex)
{
throw ex;
}
cn.Close();
}
protected void Button1_Click(object sender, EventArgs e)
{
#region fileupload
var FileExtension = Path.GetExtension(FileUpload1.PostedFile.FileName).Substring(1);
string SaveLocation = Server.MapPath("Invoices\\") + Guid.NewGuid().ToString("N") + FileExtension;
MySqlConnection connection = new MySqlConnection("server=localhost; userid=root; password=admin1234; database=admindb; allowuservariables=True");
MySqlCommand cmd = new MySqlCommand();
cmd.CommandText = "insert into invoicesfp (PicAddress), VALUES (#PicAddress)";
cmd.CommandType = CommandType.Text;
cmd.Connection = connection;
cmd.Parameters.AddWithValue("PicAddress", Server.MapPath("~/Invoices"));
cmd.Connection.Open();
cmd.BeginExecuteNonQuery();
cmd.Connection.Close();
try
{
FileUpload1.PostedFile.SaveAs(SaveLocation);
}
catch (Exception ex)
{
if (ex is ArgumentNullException || ex is NullReferenceException)
{
throw ex;
}
}
string PicAddress = "~/Invoices/" + SaveLocation;
}
#endregion
}
Update
Try this Code first, using this sample you do not need to use Rename Method And whatever its Extension is, it is supported:
#region fileupload
var FileExtension = Path.GetExtension(FileUpload1.PostedFile.FileName).Substring(1);
string SaveLocation = Server.MapPath("Invoices\\") + Guid.NewGuid().ToString("N") + "." + FileExtension;
try
{
FileUpload1.PostedFile.SaveAs(SaveLocation);
}
catch (Exception ex)
{
if (ex is ArgumentNullException || ex is NullReferenceException)
{
throw ex;
}
}
string PicAddress = "~/Invoices/" + SaveLocation;
#endregion
MySqlConnection connection = new MySqlConnection("server=localhost; userid=root; password=admin1234; database=admindb; allowuservariables=True");
MySqlCommand cmd = new MySqlCommand();
cmd.CommandText = "INSERT INTO InvoicesFP (PicAddress) VALUES (#PicAddress)";
cmd.CommandType = CommandType.Text;
cmd.Connection = connection;
cmd.Parameters.AddWithValue("PicAddress", "PicAddress");
cmd.Connection.Open();
cmd.ExecuteNonQuery();
cmd.Connection.Close();
then in your page_load you can call the Select Query to get the Address out database and pass it over to control e.g:
const string DB_CONN_STR = "Server=etc;Uid=etc;Pwd=etc;Database=etc;";
MySqlConnection cn = new MySqlConnection(DB_CONN_STR);
try {
string sqlCmd = "SELECT PicAddress FROM [YourTable] where Id == PicAddress id";
cn.Open(); // have to explicitly open connection (fetches from pool)
MySqlCommand cmd = new MySqlCommand(sqlCmd, cn);
cmd.CommandType = CommandType.Text;
MySqlDataReader rdr = cmd.ExecuteReader();
while(rdr.Read())
{
string url = rdr["Name of the Field Assuming PicAddress"].ToString();
Image1.ImageUrl = url;
}
}
catch(Exception ex)
{
throw ex;
}
Thats All - Happy Coding
I'm pretty sure that the Sql Syntax is right since it's a legit query.
However i've never stumbled on this issue before.
private void button1_Click(object sender, EventArgs e)
{
string ett = textBox1.Text;
if (ett == "")
{
MessageBox.Show("Du måste fylla i UID, vilket du finner i användarlistan.");
return;
}
try
{
if (connect.State == ConnectionState.Open)
{
MySqlCommand cmd = new MySqlCommand();
cmd.Connection = connect;
cmd.CommandText = "DELETE FROM Users WHERE uid = #uid";
cmd.Parameters.AddWithValue("#uid", textBox1.Text);
MySqlDataReader accessed = cmd.ExecuteReader();
MessageBox.Show("Användaren borttagen.");
}
else
{
MessageBox.Show("Något gick tyvärr fel, kontakta systemadministratören.");
}
}
catch (Exception ex)
{
{ MessageBox.Show(ex.Message); }
}
}
The problem may be related to this:
{
MySqlCommand cmd = new MySqlCommand();
cmd.Connection = connect;
cmd.CommandText = "DELETE FROM Users WHERE uid = #uid";
cmd.Parameters.AddWithValue("#uid", textBox1.Text);
MySqlDataReader accessed = cmd.ExecuteReader();
MessageBox.Show("Användaren borttagen.");
}
try
{
MySqlCommand cmd = new MySqlCommand();
cmd.Connection = connect;
cmd.CommandType = CommandType.Text
cmd.CommandText = "DELETE FROM Users WHERE uid = #uid";
cmd.Parameters.AddWithValue("#uid", textBox1.Text);
cmd.ExecuteNonQuery
MessageBox.Show("Användaren borttagen.");
}
Now you've shown us your whole code in the comments, the problem is obvious.
You have written a method to initialise, set up and open your database connection; and this other method which runs on a button click, which uses it.
However, nowhere in your code do you call the method which initialises your database connection, therefore it is not set up when you try to use it - obvious really.
I can see you think you are checking to see if the connection is working by checking its State property, but calling any sort of method or property accessor on an uninitialised reference type won't work, you'll get the NullReferenceException you've been getting.
To fix, call the connection set up method from your button press, before trying to use the connection:
private void button1_Click(object sender, EventArgs e)
{
string ett = textBox1.Text;
if (ett == "")
{
MessageBox.Show("Du måste fylla i UID, vilket du finner i användarlistan.");
return;
}
try
{
db_connection(); //added this line
if (connect.State == ConnectionState.Open)
{
MySqlCommand cmd = new MySqlCommand();
cmd.Connection = connect;
cmd.CommandText = "DELETE FROM Users WHERE uid = #uid";
cmd.Parameters.AddWithValue("#uid", textBox1.Text);
MySqlDataReader accessed = cmd.ExecuteReader();
MessageBox.Show("Användaren borttagen.");
}
else
{
MessageBox.Show("Något gick tyvärr fel, kontakta systemadministratören.");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
You have not defined the variable, "connect".
I want to change password that saved in db,but my code dose not work. what is wrong? I always see the last message:
unable to connect database
public partial class pws : System.Web.UI.Page
{
static string strcon = (System.Web.Configuration.WebConfigurationManager.ConnectionStrings["strcon"].ConnectionString);
protected void Page_Load(object sender, EventArgs e)
{
}
private void ShowPopUpMsg(string msg)
{
StringBuilder sb = new StringBuilder();
sb.Append("alert('");
sb.Append(msg.Replace("\n", "\\n").Replace("\r", "").Replace("'", "\\'"));
sb.Append("');");
ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "showalert", sb.ToString(), true);
}
protected void btnInsert_Click(object sender, EventArgs e)
{
try {
SqlConnection db = new SqlConnection(strcon);
db.Open();
string strId = string.Empty;
string strusername = string.Empty;
string OLdpassword = string.Empty;
SqlCommand cmd;
cmd = new SqlCommand("SELECT * FROM login WHERE login_username =#login_username ", db);
cmd.Parameters.AddWithValue("login_username", txtOldUsername.Text);
cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
cmd.Dispose();
cmd = null;
db.Close();
db.Open();
SqlDataReader DR;
DR = cmd.ExecuteReader();
if (DR.Read())
{
strId = DR["login_id"].ToString();
strusername = DR["login_username"].ToString();
OLdpassword = DR["login_Password"].ToString();
}
db.Close();
if (OLdpassword == txtOldPass.Text)
{
db.Open();
string Command = "Update login Set login_Password= #login_Password WHERE login_username=#login_username";
SqlCommand cmdIns = new SqlCommand(Command, db);
cmdIns.Parameters.AddWithValue("#login_Password ", txtNewPass.Text);
cmdIns.Parameters.AddWithValue("#login_username ", txtOldUsername.Text);
cmdIns.ExecuteNonQuery();
cmdIns.Parameters.Clear();
cmdIns.Dispose();
cmdIns = null;
db.Close();
ShowPopUpMsg("successful");
}
else
{
ShowPopUpMsg(" old pass is not correct");
}
}
catch
{
ShowPopUpMsg("unable to connect database");
}
}
}
this part:
cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
cmd.Dispose();
cmd = null;
db.Close();
db.Open();
SqlDataReader DR;
DR = cmd.ExecuteReader();
why do you execute a non query, which is a query (select * from ...)?
why do you dispose the SqlCommand object cmd and why do you reuse it after disposing?
why do you close and open the line below?
I would rewrite those lines it like this:
SqlDataReader DR = cmd.ExecuteReader();
I would recomment a using statement or closing the connection in a finally block:
SqlConnection db = new SqlConnection(strcon);
try{
db.Open();
//.... the rest
}
catch(Exception ex)
{
ShowPopUpMsg("unable to connect database: " + ex.Message);
}
finally
{
db.Close();
}
and another thing: I would use the primary key in the update statement. where id = login_id instead of the username. unless the username is set to "unique"
Check if you can connect to the database using your credentials and database management tool (I assume you you use MS SQL Server so use MS SQL Server Management Studio)
Check if the format of your connection string is correct. You can use this website http://www.connectionstrings.com/ to do it.
I hope this will help you.
Try to step through the code and find where the exception occures, and look at the details of the exception.
My guess is that there are something wrong with you connection string (strcon).
i have question. I want to store data on my mysqldatabase using this C#
private void btnSaveFilm_Click(object sender, EventArgs e)
{
try
{
MySqlConnection conn = new MySqlConnection(connection.mysqlconnectionbuilder());
conn.Open();
MySqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "INSERT INTO film(judul,genre,asal,kondisi)"
+ "VALUES(#judul,#genre,#asal,#kondisi)";
cmd.CommandType = CommandType.Text;
cmd.Parameters.AddWithValue("#judul", textBoxJudul.Text);
cmd.Parameters.AddWithValue("#genre", category(comboBoxGenre.SelectedValue.ToString()).ToString());
cmd.Parameters.AddWithValue("#asal", asal(comboBoxAsal.SelectedValue.ToString()).ToString());
cmd.Parameters.AddWithValue("#kondisi", checkedStatus());
cmd.ExecuteNonQuery();
conn.Close();
}
catch(Exception exe)
{
Console.Write("Error on Save Film : " + exe.ToString() + "\n" +exe.Message);
}
}
but it shows error System.NullReferenceException: Object reference not set to an instance of an object.
Error at this line 40:
cmd.Parameters.AddWithValue("#genre",kategori(comboBoxGenre.SelectedValue.ToString()).ToString());
how to solve that?
refractor your code into this, use using statement,
string connString = connectionmysqlconnectionbuilder();
using (MySqlConnection conn = new MySqlConnection(connString)
{
using (MySqlCommand cmd = new MySqlCommand())
{
cmd.Connection = conn;
cmd.CommandText = #"INSERT INTO film(judul,genre,asal,kondisi)
VALUES(#judul,#genre,#asal,#kondisi)";
cmd.Parameters.AddWithValue("#judul", textBoxJudul.Text);
cmd.Parameters.AddWithValue("#genre", kategori(comboBoxGenre.Text).ToString());
cmd.Parameters.AddWithValue("#asal", asal(comboBoxAsal.Text).ToString());
cmd.Parameters.AddWithValue("#kondisi", checkedStatus());
try
{
comm.Open();
cmd.ExecuteNonQuery();
}
catch(MySqlException ex)
(
Console.WriteLine(ex.ToString());
)
}
}
you could also use
comboBoxGenre.Text instead of comboBoxGenre.SelectedValue
There can be two reasons:
1.comboBoxGenre.SelectedValue will be null
2.kategori() will be returning null
you can handle null error by using Convert.ToString() instead of variable.toString()
so use this instead also for other lines
cmd.Parameters.AddWithValue("#genre", Convert.ToString(kategori(Convert.ToString(comboBoxGenre.SelectedValue))));
i have cut and paste buttons while cutting i have one sql operation and while pasting one sql operation . how to use transation statement for this .
protected void btnCut_Click(object sender, EventArgs e)
{
hidCutnode.Value = TreeView2.SelectedNode.Value;
string sqlQuery = "update CUSTOMIZEDTREE set parentid='" + 0 + "' where nodeid='" + hidCutnode.Value + "'";
string connectionString = "Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=10.69.200.62)(PORT=1521)))(CONNECT_DATA=(SID=orcl)));User Id=apex_demo;Password=apex_demo;";
OracleConnection con = new OracleConnection(connectionString);
con.Open();
tran = con.BeginTransaction();
OracleCommand cmd = new OracleCommand(sqlQuery, con);
cmd.Transaction = tran;
cmd.ExecuteNonQuery();
con.Close();
}
protected void btnPaste_Click(object sender, EventArgs e)
{
hidPastenode.Value = TreeView2.SelectedNode.Value;
try
{
string sqlQuery = "update CUSTOMIZEDTREE set parentid='" + hidPastenode.Value + "' where nodeid='" + hidCutnode.Value + "'";
string connectionString = "Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=10.69.200.62)(PORT=1521)))(CONNECT_DATA=(SID=orcl)));User Id=apex_demo;Password=apex_demo;";
OracleConnection con = new OracleConnection(connectionString);
con.Open();
OracleCommand cmd = new OracleCommand(sqlQuery, con);
tran = con.BeginTransaction();
// cmd.Connection = con;
cmd.Transaction = tran;
cmd.ExecuteNonQuery();
tran.Commit();
con.Close();
PopulateCustomTree();
}
catch (Exception ex)
{
tran.Rollback();
ex.ToString();
}
}
Pass transaction object as function parameter to the second method and dont commit in method1. Use BeginTransaction in first method only.
SqlTransaction trn = connect.BeginTransaction();
try
{
SqlCommand command = new SqlCommand(query);
command.Transaction = trn;
command.Connection = connect;
connect.Open();
command.CommandTimeout = 0;
command.ExecuteNonQuery();
trn.Commit();
}
catch (Exception ex)
{
trn.Rollback();
}
connect.Close();