When I click acceptBTN I'd like to update the Quantity of a certain Item in the stockTBL
private void acceptBTN_Click(object sender, EventArgs e)
{
string constring = #"Data Source=|DataDirectory|\LWADataBase.sdf";
string Query = "UPDATE stockTBL SET Quantity = Quantity+ '" + this.quantityTxt.Text + "' where [Item Name] = '" + this.itemTxt.Text + "';";
SqlCeConnection conDataBase = new SqlCeConnection(constring);
SqlCeCommand cmdDataBase = new SqlCeCommand(Query, conDataBase);
try
{
conDataBase.Open();
MessageBox.Show("Sucess");
//displays a system error message if a problem is found
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
This is my code, when I click the acceptBTN it just displays the MessageBox without updating the quantity.
You didn't even execute the query you just created it.Try to execute it first
conDataBase.Open();
cmdDataBase.ExecuteNonQuery();
conDataBase.Close();
Some suggestions:
Try using parameterized queries instead of string concatenation to avoid SQL Injection attacks.
Always use using statements for disposable objects in order to make sure they are properly disposed.
string constring = #"Data Source=|DataDirectory|\LWADataBase.sdf";
string Query = "UPDATE stockTBL SET Quantity = Quantity + #quantity where [Item Name] = #name";
using(SqlCeConnection conDataBase = new SqlCeConnection(constring))
using(SqlCeCommand cmdDataBase = new SqlCeCommand(Query, conDataBase))
{
cmdDataBase.Parameters.AddWithValue("#quantity", int.Parse(quantityTxt.Text));
cmdDataBase.Parameters.AddWithValue("#name", itemTxt.Text);
conDataBase.Open();
cmdDataBase.ExecuteNonQuery();
cmdDataBase.Close();
}
You probably want cmdDataBase.ExecuteNonQuery. You opened the connection but never executed the query.
MSDN Referece.
Related
I know plenty of people have these issues, and I've actually tried to implement some of the suggestions to my code, however I'm getting errors that just don't make sense to me. This is my first time implementing database calls to my code. Can someone please tell me what I'm doing wrong? The following error pops up: ERROR: Invalid object name 'Main'. This is actually triggered by my exception so at least something is working. Otherwise, I don't know what the issue is. On the DB end, I have (username VARCHAR, email VARCHAR and number NCHAR) Please see the code below
static string path = Path.GetFullPath(Environment.CurrentDirectory);
static string databaseName = "u_DB.mdf";
string connectionString = #"Data Source=(localdb)\MSSQLLocalDB;AttachDbFilename=" + path + #"\" + databaseName + "; Integrated Security=True;";
private void button1_Click(object sender, EventArgs e)
{
// string query = "INSERT INTO UserInfo '" + textBox1.Text + "' and password = '" + textBox2.Text + "'";
string query = "insert into Main ([username], [email], [number]) values(#username,#email,#number)";
using (SqlConnection con = new SqlConnection(connectionString))
{
try
{
con.Open();
using (SqlCommand cmd = new SqlCommand(query, con))
{
cmd.Parameters.Add("#username", SqlDbType.VarChar).Value = textBox3.Text;
cmd.Parameters.Add("#email", SqlDbType.VarChar).Value = textBox2.Text;
cmd.Parameters.AddWithValue("#number", SqlDbType.VarChar).Value = textBox1.Text;
int rowsAdded = cmd.ExecuteNonQuery();
if (rowsAdded > 0)
MessageBox.Show("Added to Database");
else
MessageBox.Show("Nothing was added");
}
}
catch (Exception ex)
{
MessageBox.Show("ERROR: " + ex.Message);
}
con.Close();
}
}
Firstly, as Chetan assumed, do you have a main table?
The syntax of the query you are using is :
INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);
Furthermore,
AddWithValue(string parameterName, object value (<== The actual value to insert!));
in your case
AddWithValue("#number", textBox1.Text);
is enough.
i have a button that when clicked inserts data from textbox and combobox fields into database tables, but every time i insert it gives me "Invalid attempt to call read when reader is closed". How can i get rid of this error. And tips on optimising the code are welcome, because i know im a total noob. thanks
private void btnSave_Click(object sender, RoutedEventArgs e)
{
try
{
SqlConnection sqlCon = new SqlConnection(#"Data Source=(localdb)\mssqllocaldb; Initial Catalog=Storagedb;");
sqlCon.Open();
string Query1 = "insert into location(Storage, Shelf, columns, rows) values(" + txtWarehouse.Text + ", " + txtShelf.Text + ", " + txtColumn.Text + ", " + txtRow.Text + ")";
SqlCommand sqlCmd = new SqlCommand(Query1, sqlCon);
SqlDataAdapter dataAdp = new SqlDataAdapter(sqlCmd);
dataAdp.SelectCommand.ExecuteNonQuery();
sqlCon.Close();
}
catch (Exception er)
{
MessageBox.Show(er.Message);
}
try
{
SqlConnection sqlCon = new SqlConnection(#"Data Source=(localdb)\mssqllocaldb; Initial Catalog=Storagedb;");
sqlCon.Open();
string Query3 = "SELECT LOCATION_ID FROM LOCATION WHERE storage='" + txtWarehouse.Text + "' AND shelf='" + txtShelf.Text + "' AND columns='"
+ txtColumn.Text + "' AND rows='" + txtRow.Text + "'";
SqlCommand sqlCmd1 = new SqlCommand(Query3, sqlCon);
SqlDataReader dr = sqlCmd1.ExecuteReader(); ;
while (dr.Read())
{
string LocationId = dr[0].ToString();
dr.Close();
string Query2 = "insert into product(SKU, nimetus, minimum, maximum, quantity,location_ID,category_ID,OrderMail_ID) values ('" + txtSku.Text + "','" + txtNimetus.Text + "', '"
+ txtMin.Text + "', '" + txtMax.Text + "', '" + txtQuan.Text + "', '" + LocationId + "', '" + (cbCat.SelectedIndex+1) + "', '" + (cbMail.SelectedIndex+1) + "')";
SqlCommand sqlCmd = new SqlCommand(Query2, sqlCon);
SqlDataAdapter dataAdp = new SqlDataAdapter(sqlCmd);
dataAdp.SelectCommand.ExecuteNonQuery();
}
sqlCon.Close();
}
catch (Exception ed)
{
MessageBox.Show(ed.Message);
}
}
Let's try to make some adjustments to your code.
First thing to consider is to use a parameterized query and not a
string concatenation when you build an sql command. This is mandatory
to avoid parsing errors and Sql Injections
Second, you should encapsulate the disposable objects in a using statement
to be sure they receive the proper disposal when you have finished to
use them.
Third, you can get the LOCATION_ID from your table without running a
separate query simply adding SELECT SCOPE_IDENTITY() as second batch to your first command. (This works only if you have declared the LOCATION_ID field in the first table as an IDENTITY column)
Fourth, you put everything in a transaction to avoid problems in case
some of the code fails unexpectedly
So:
SqlTransaction tr = null;
try
{
string cmdText = #"insert into location(Storage, Shelf, columns, rows)
values(#storage,#shelf,#columns,#rows);
select scope_identity()";
using(SqlConnection sqlCon = new SqlConnection(.....))
using(SqlCommand cmd = new SqlCommand(cmdText, sqlCon))
{
sqlCon.Open();
using( tr = sqlCon.BeginTransaction())
{
// Prepare all the parameters required by the command
cmd.Parameters.Add("#storage", SqlDbType.Int).Value = Convert.ToInt32(txtWarehouse.Text);
cmd.Parameters.Add("#shelf", SqlDbType.Int).Value = Convert.ToInt32(txtShelf.Text);
cmd.Parameters.Add("#columns", SqlDbType.Int).Value = Convert.ToInt32(txtColumn.Text );
cmd.Parameters.Add("#rows", SqlDbType.Int).Value = Convert.ToInt32(txtRow.Text);
// Execute the command and get back the result of SCOPE_IDENTITY
int newLocation = Convert.ToInt32(cmd.ExecuteScalar());
// Set the second command text
cmdText = #"insert into product(SKU, nimetus, minimum, maximum, quantity,location_ID,category_ID,OrderMail_ID)
values (#sku, #nimetus,#min,#max,#qty,#locid,#catid,#ordid)";
// Build a new command with the second text
using(SqlCommand cmd1 = new SqlCommand(cmdText, sqlCon))
{
// Inform the new command we are inside a transaction
cmd1.Transaction = tr;
// Add all the required parameters for the second command
cmd1.Parameters.Add("#sku", SqlDbType.NVarChar).Value = txtSku.Text;
cmd1.Parameters.Add("#nimetus",SqlDbType.NVarChar).Value = txtNimetus.Text;
cmd1.Parameters.Add("#locid", SqlDbType.Int).Value = newLocation;
.... and so on for the other parameters required
cmd1.ExecuteNonQuery();
// If we reach this point the everything is allright and
// we can commit the two inserts together
tr.Commit();
}
}
}
}
catch (Exception er)
{
// In case of exceptions do not insert anything...
if(tr != null)
tr.Rollback();
MessageBox.Show(er.Message);
}
Notice that in the first command I use parameters of type SqlDbType.Int because you haven't used single quotes around your text. This should be verified against the real data type of your table columns and adjusted to match the type. This is true as well for the second command where you put everything as text albeit some of those fields seems to be integer (_location_id_ is probably an integer). Please verify against your table.
I am making a student database which contain the course id, course name, credits of each course, pass fail statement and the grades. Now I want to get the sum of the grades in a button and make them appear on a textbox. this is the code I wrote, but it's giving me an error saying the sum function doesn't exist. What should I do?
private void button1_Click(object sender, EventArgs e)
{
string ConString = " datasource = localhost; port = 3306; username = root; password = 3306";
string Query = " Select sum (grade) form studentdata.semestre1";
MySqlConnection ConDatabase = new MySqlConnection(ConString);
MySqlCommand cmdDataBase = new MySqlCommand(Query, ConDatabase);
MySqlDataReader myReader;
ConDatabase.Open();
myReader = cmdDataBase.ExecuteReader() ;
while (myReader.Read())
{
textBox2.Text = myReader.GetString(0);
}
myReader.Close();
Two reasons:
SQL query should not have space between the function and the column name
Change your query from "Form" to "FROM"
string Query = "Select SUM(grade) FROM studentdata.semestre1";
Try:
SELECT SUM(grade) FROM studentdata.semestre1
The most important change is the from.
For a more complete fix; add using, and use ExecuteScalar here:
using(MySqlConnection ConDatabase = new MySqlConnection(ConString))
using(MySqlCommand cmdDataBase = new MySqlCommand(
"SELECT SUM(grade) FROM studentdata.semestre1", ConDatabase))
{
ConDatabase.Open();
textBox2.Text = Convert.ToString(cmdDataBase.ExecuteScalar());
}
I want to perform 2 queries in one button click. I tried the
string query = "first query";
query+="second query";
But this didn't work it shows error.
I have now created 2 separate connections like below:
try
{
SqlConnection conn1 = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionStringDatabase"].ConnectionString);
//open connection with database
conn1.Open();
//query to select all users with teh given username
SqlCommand com1 = new SqlCommand("insert into artikulli (tema,abstrakti, kategoria_id, keywords ) values (#tema, #abstrakti, #kategoria, #keywords)", conn1);
// comand.Parameters.AddWithValue("#id", iD);
com1.Parameters.AddWithValue("#tema", InputTitle.Value);
com1.Parameters.AddWithValue("#abstrakti", TextareaAbstract.Value);
com1.Parameters.AddWithValue("#kategoria", DropdownCategory.Value);
com1.Parameters.AddWithValue("#keywords", InputTags.Value);
//execute queries
com1.ExecuteNonQuery();
conn1.Close();
if (FileUploadArtikull.HasFile)
{
int filesize = FileUploadArtikull.PostedFile.ContentLength;
if (filesize > 4194304)
{
ScriptManager.RegisterStartupScript(this, this.GetType(), "popup", "alert('Maximumi i madhesise eshte 4MB');", true);
}
else
{
string filename = "artikuj/" + Path.GetFileName(FileUploadArtikull.PostedFile.FileName);
SqlConnection conn2 = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionStringDatabase"].ConnectionString);
SqlCommand com2 = new SqlCommand("insert into artikulli(path) values ('" + filename + "')", conn2);
//open connection with database
conn2.Open();
com2.ExecuteNonQuery();
FileUploadArtikull.SaveAs(Server.MapPath("~/artikuj\\" + FileUploadArtikull.FileName));
Response.Redirect("dashboard.aspx");
}
}
else
{
ScriptManager.RegisterStartupScript(this, this.GetType(), "popup", "alert('Ju nuk keni perzgjedhur asnje file');", true);
}
}
But the problem is that only the second query is performed and the firs is saved as null in database
In your case, there is no reason to open two connections. In addition, the C# language has evolved, so I recommend using the power given by the new language constructs (using, var).
Here is an improved version that should work assuming that the values you bind to your parameters are valid:
try
{
using(var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionStringDatabase"].ConnectionString))
{
//open connection with database
connection.Open();
//query to select all users with teh given username
using(var command1 = new SqlCommand("insert into artikulli (tema,abstrakti, kategoria_id, keywords ) values (#tema, #abstrakti, #kategoria, #keywords)", connection))
{
command1.Parameters.AddWithValue("#tema", InputTitle.Value);
command1.Parameters.AddWithValue("#abstrakti", TextareaAbstract.Value);
command1.Parameters.AddWithValue("#kategoria", DropdownCategory.Value);
command1.Parameters.AddWithValue("#keywords", InputTags.Value);
//execute first query
command1.ExecuteNonQuery();
}
//build second query
string filename = "artikuj/" + Path.GetFileName(FileUploadArtikull.PostedFile.FileName);
using(SqlCommand command2 = new SqlCommand("insert into artikulli(path) values (#filename)", connection))
{
//add parameters
command2.Parameters.AddWithValue("#filename", filename);
//execute second query
command2.ExecuteNonQuery();
}
}
}
//TODO: add some exception handling
//simply wrapping code in a try block has no effect without a catch/finally
Try below code, No need to open the connection twice
string query1 = "insert into artikulli (tema,abstrakti, kategoria_id, keywords ) values (#tema, #abstrakti, #kategoria, #keywords)";
SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionStringDatabase"].ConnectionString);
SqlCommand com1= new SqlCommand(query1, conn);
com1.Parameters.AddWithValue("#tema", InputTitle.Value);
com1.Parameters.AddWithValue("#abstrakti", TextareaAbstract.Value);
com1.Parameters.AddWithValue("#kategoria", DropdownCategory.Value);
com1.Parameters.AddWithValue("#keywords", InputTags.Value);
string query2 = "insert into artikulli(path) values ('" + filename + "')", conn);
comm.ExecuteNonQuery();
comm.CommandText = query2;
comm.ExecuteScalar();
Currently this code only shows the value of the "id" in database, how do i make it so it shows both "id" and "name" values in same row, like "5 - John Carpenter" ?
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string constring = "datasource=localhost;port=3306;username=root;password=rootpassword";
string Query = "select * from database2.employee where id='" + comboBox1.Text + "' ORDER BY Auto ;";
MySqlConnection conDataBase = new MySqlConnection(constring);
MySqlCommand cmdDataBase = new MySqlCommand(Query, conDataBase);
MySqlDataReader myReader;
1. use parametrised queries to avoid SQL injection attacks.
2. call Read() function on MySqlDataReader Object to read the select query results.
3. use comboBox1.SelectedItem.ToString() instead of ComboBox1.Text to get the selected Item from combobox.
Try This:
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string constring = "datasource=localhost;port=3306;username=root;password=rootpassword";
string Query = "select * from database2.employee where id=#id ORDER BY Auto ;";
MySqlConnection conDataBase = new MySqlConnection(constring);
MySqlCommand cmdDataBase = new MySqlCommand(Query, conDataBase);
cmdDataBase.Parameters.AddWithValue("#id",comboBox1.SelectedItem.ToString());
MySqlDataReader myReader=cmdDataBase.ExecuteReader();
if(myReader.Read())
{
TextBox1.Text=myReader["id"].ToString() +" - "+myReader["name"].ToString();
}
conDataBase.Close();
}