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Connection is not closed properly ASP.NET C#

I have this button click event. Been trying to replace the con.Close() in different lines of code, tried for hours but couldn't fix. Maybe a second pair of eyes can help?
Error: System.InvalidOperationException: 'The connection was not closed. The connection's current state is open.'
protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
con.Open();
string query = "SELECT CATEGORY FROM CATEGORY WHERE C_UserName = '" + Session["id"] + "' AND CATEGORY = '" + DropDownList1.SelectedItem.Value + "' ";
SqlCommand cmd = new SqlCommand(query, con);
SqlDataReader reader = cmd.ExecuteReader();
if (reader.HasRows)
{
cmd.Parameters.AddWithValue("#CATEGORY", DropDownList1.SelectedItem.Value);
lblResult.Text = "You have selected this category. Please select a new category";
con.Close();
}
else
{
SqlCommand cmd1 = new SqlCommand("UPDATE SET CATEGORY CCID#CCID (CATEGORY, C_USERNAME, CCID) VALUES (#CATEGORY, #C_USERNAME, #CCID)", con);
cmd1.Parameters.AddWithValue("CATEGORY", DropDownList1.SelectedItem.Value);
cmd1.Parameters.AddWithValue("C_USERNAME", Session["id"]);
cmd1.Parameters.AddWithValue("CCID", Label1.Text);
con.Open();
int i = cmd1.ExecuteNonQuery();
con.Close();
if (i != 0)
{
Label2.Text = " Your data is been saved in the database";
Label2.ForeColor = System.Drawing.Color.ForestGreen;
}
else
{
Label2.Text = "Something went wrong with selection";
Label2.ForeColor = System.Drawing.Color.Red;
}
}
}

Try this (open connection only once and close only once):
protected void Button1_Click(object sender, EventArgs e) {
using(SqlConnection con = new SqlConnection()) {
con.ConnectionString = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
string query = "SELECT CATEGORY FROM CATEGORY WHERE C_UserName = '" + Session["id"] + "' AND CATEGORY = '" + DropDownList1.SelectedItem.Value + "' ";
SqlCommand cmd = new SqlCommand(query, con);
con.Open();
SqlDataReader reader = cmd.ExecuteReader();
bool hasRows = reader.HasRows;
reader.Close();
if (hasRows) {
// This line makes no sense after the execution of the query.
//cmd.Parameters.AddWithValue("#CATEGORY", DropDownList1.SelectedItem.Value);
lblResult.Text = "You have selected this category. Please select a new category";
} else {
SqlCommand cmd1 = new SqlCommand("UPDATE SET CATEGORY CCID#CCID (CATEGORY, C_USERNAME, CCID) VALUES (#CATEGORY, #C_USERNAME, #CCID)", con);
cmd1.Parameters.AddWithValue("CATEGORY", DropDownList1.SelectedItem.Value);
cmd1.Parameters.AddWithValue("C_USERNAME", Session["id"]);
cmd1.Parameters.AddWithValue("CCID", Label1.Text);
int i = cmd1.ExecuteNonQuery();
if (i != 0) {
Label2.Text = " Your data is been saved in the database";
Label2.ForeColor = System.Drawing.Color.ForestGreen;
} else {
Label2.Text = "Something went wrong with selection";
Label2.ForeColor = System.Drawing.Color.Red;
}
}
con.Close();
}
}
Now let's discuss this line
string query = "SELECT CATEGORY FROM CATEGORY WHERE C_UserName = '" + Session["id"] + "' AND CATEGORY = '" + DropDownList1.SelectedItem.Value + "' ";
This let's attacker manipulate your input with sql injection. To solve this, use the same cmd1.Parameters.AddWithValue("CATEGORY", DropDownList1.SelectedItem.Value); that you are using in the second query. The Session["id"] is somewhat safer as it is not provided by the user but better safe than sorry as the parameters sanitize the input and protect you from sql injection.

Error in gridviewUpdating asp.net with a timestamp update

I have two buttons, SetIn and SetOut. They both have the commandName UPDATE ( I have two buttons as I'd like the text to be different on the button depending on the value of one field in the row.
I'm getting a problem in that when I run the update SQL statement, it throws an error at me. It says:
An exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll but was not handled in user code
Additional information: Incorrect syntax near '14'.
This means that there is an issue with the date and time stamp that I am trying to update the row with (I'm making the update at 14.02pm).
My aspx.cs page code is:
protected void GridView1_RowUpdating(object sender, System.Web.UI.WebControls.GridViewUpdateEventArgs e)
{
Label id = GridView1.Rows[e.RowIndex].FindControl("lbl_Index") as Label;
int rowToUpdate = Int32.Parse(id.Text);
con = new SqlConnection(cs);
int scopeValue;
con = new SqlConnection(cs);
cmd = new SqlCommand();
cmd.CommandText = "SELECT in_scope FROM " + databaseName + " WHERE id = '" + rowToUpdate + "'";
cmd.Parameters.AddWithValue("#id", rowToUpdate);
cmd.Connection = con;
try
{
con.Open();
scopeValue = Convert.ToInt32(cmd.ExecuteScalar());
//database_entries.Text = recordCount.ToString();
}
finally
{
con.Close();
}
string modifiedBy = userManagement.getWeldID();
string updateDate = DateTime.UtcNow.ToString("dd/MMM/yyyy HH:mm:ss");
{
if (scopeValue == 1)
{
// Label id = GridView1.Rows[e.RowIndex].FindControl("lbl_Index") as Label;
string sqlStatement = "";
con = new SqlConnection(cs);
// SqlCommand cmd = new SqlCommand();
sqlStatement = #"update dbo.Fair_Use_InScope_MIF_Alex_temp set in_scope = '0', modified_by = " + modifiedBy + ", date_updated = " + updateDate + " where id = '" + rowToUpdate + "'";
con.Open();
cmd = new SqlCommand(sqlStatement, con);
cmd.ExecuteNonQuery();
con.Close();
ShowData();
}
if (scopeValue == 0)
{
// Label id = GridView1.Rows[e.RowIndex].FindControl("lbl_Index") as Label;
string sqlStatement = "";
con = new SqlConnection(cs);
// SqlCommand cmd = new SqlCommand();
sqlStatement = #"update dbo.Fair_Use_InScope_MIF_Alex_temp set in_scope = '1', modified_by = " + modifiedBy + ", date_updated = " + updateDate + " where id = '" + rowToUpdate + "'";
con.Open();
cmd = new SqlCommand(sqlStatement, con);
cmd.ExecuteNonQuery();
con.Close();
ShowData();
}
}
}
I'm basically trying to get the scopeValue (0 or 1) of the row, and if the Update command is called, and the scopeValue was previously 0, set it to 1 now and vice versa. I also need to update the time that the change was made and who made the change in that row. (these are both displayed in the gridview)
Any help would be much appreciated as I am a beginner to ASP.NET and C# and SQL SERVER!!

You are sending a DateTime as a string (without even enclosing single quotes date_updated = '" + updateDate + "') and that will always cause problems.
It's better to use parameters in your query. This prevents SQL injection, improves readability, ensures type safety, no more worries about the correct use of quotation marks etc.
string sqlStatement = "UPDATE dbo.Fair_Use_InScope_MIF_Alex_temp SET in_scope = 0, modified_by = #modifiedBy, date_updated = #updateDate WHERE (id = #rowToUpdate)";
using (SqlConnection connection = new SqlConnection(cs))
using (SqlCommand command = new SqlCommand(sqlStatement, connection))
{
command.Parameters.Add("#modifiedBy", SqlDbType.VarChar).Value = modifiedBy;
command.Parameters.Add("#updateDate", SqlDbType.DateTime).Value = DateTime.Now;
command.Parameters.Add("#rowToUpdate", SqlDbType.Int).Value = 35;
connection.Open();
command.ExecuteNonQuery();
}

Want to create a comment system in asp.net

i am coding for a commenting system in asp.net C# but i am stopped at delete command because of i am not using any type of serial numbers to comments posted, then how can i able to delete a specific comment, i am just using a username, date, time, and text in comment. Can anyone help me please that how to use a delete command in this condition??
here is my code for posting:
protected void pospost_Click(object sender, EventArgs e)
{
string login;
if (HttpContext.Current.Session["UserName"] != null)
{
login = HttpContext.Current.Session["UserName"].ToString();
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandText = "select * from mobiles_pos";
da = new SqlDataAdapter(cmd);
ds = new DataSet();
da.Fill(ds);
DataRow rw = ds.Tables[0].NewRow();
rw[0] = Model.Text.ToString();
rw[1] = titlepos.Text.ToString();
rw[2] = txtpos.Text.ToString();
rw[3] = DateTime.Today.Date.ToString();
rw[4] = DateTime.Now.TimeOfDay.ToString();
rw[5] = login.ToString();
ds.Tables[0].Rows.Add(rw);
SqlCommand cmd1 = new SqlCommand();
cmd1.Connection = con;
cmd1.CommandText = "insert into mobiles_pos values('" + Model.Text + "','" + titlepos.Text + "','" + txtpos.Text + "','" + DateTime.Today.Date + "','" + DateTime.Now.TimeOfDay + "','" + login + "')";
da.InsertCommand = cmd1;
da.Update(ds);
con.Close();
titlepos.Text = "";
txtpos.Text = "";
//DataList2.DataSource = ds;
//DataList2.DataBind();
BindDataList2();
}
}

Best - Add a Primary key to the "mobiles_pos" table since your using sql just use an identity field it will auto increment for you.
or
Quick - Use a combination of the User name and date comment was intered you must use the full date time or it will delete everything that user entered that day.
"Delete from mobiles_pos where username = #UserName and createdDate = #createdDate"

How do I delete a row from a Microsoft Access table using c#

I've tried this code:
string sql = " DELETE FROM HotelCustomers WHERE [Room Number] =" + textBox1.Text;
OleDbConnection My_Connection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source= c:\\Users\\Documents\\HotelCustomersOld.mdb");
My_Connection.Open();
OleDbCommand My_Command = new OleDbCommand(sql, My_Connection);
My_Command.ExecuteNonQuery();
Error: Data type mismatch in criteria expression, at the line:
My_Command.ExecuteNonQuery();

Use parametrized query to avoid all kind of errors
string sql = " DELETE FROM HotelCustomers WHERE [Room Number] =?";
using(OleDbConnection My_Connection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source= c:\\Users\\Documents\\HotelCustomersOld.mdb"))
{
My_Connection.Open();
OleDbCommand My_Command = new OleDbCommand(sql, My_Connection);
My_Command.Parameters.Add("#p1", textBox1.Text);
My_Command.ExecuteNonQuery();
}
In your case the Room NUmber field is of Text type so, you need to enclose the value in single quotes, but this is really wrong. You expose your code to maliciuos text written by your user inside the text box. A very simple and funny example here

Which type is your [Room Number] column? If it is a string then you have to write the value with inverted comma or quotation mark (I'm not sure which of both is used in Access).
string sql = " DELETE FROM HotelCustomers WHERE [Room Number] = '" + textBox1.Text + "'";
To avoid SQL injektion you should use Parameters instead of the string operation.

public static void DeleteLine(string kv)
{
OleDbConnection myConnection = GetConnection();
string myQuery = "DELETE FROM Cloth WHERE [ClothName] = '" + kv + "'";
OleDbCommand myCommand = new OleDbCommand(myQuery, myConnection);
try
{
myConnection.Open();
myCommand.ExecuteNonQuery();
}
catch (Exception ex)
{
Console.WriteLine("Exception in DBHandler", ex);
}
finally
{
myConnection.Close();
}
}

try
{
OleDbConnection con = new OleDbConnection("provider = microsoft.ace.oledb.12.0;data source = E:\\Sohkidatabase\\Sohki.accdb");
con.Open();
str = "select * from compny_info where id=" + comboBox1.Text.Trim() + "";
com = new OleDbCommand(str, con);
OleDbDataReader reader = com.ExecuteReader();
if (reader.Read())
{
textBox1.Text = reader["regis_no"].ToString();
textBox2.Text = reader["comp_oner"].ToString();
textBox3.Text = reader["comp_name"].ToString();
textBox4.Text = reader["comp_add"].ToString();
textBox5.Text = reader["tin_no"].ToString();
textBox6.Text = reader["email"].ToString();
}
con.Close();
reader.Close();
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}

public static void DeleteLine(string kv) {
OleDbConnection myConnection = GetConnection();
string myQuery = "DELETE FROM Cloth WHERE [ClothName] = '" + kv + "'" ;
}

create new DataBase & fill with another DataBase

I have a Problem in C# windows program that is I can't work with 2 database those are
simple database in tables and Data. in this Project I want to open Access DataBase and Create New Access DataBase with another Name But with Same Tables And Columns And Rows and fill with Source Data that is in Source Database.
I can't read from source DB and insert into new destination DataBase. the sorce code is below please Help me to Complete this Project, thanks a lot.
private void button3_Click(object sender, EventArgs e)
{
OleDbConnection cn = new OleDbConnection();
cn.ConnectionString = #"provider=Microsoft.ACE.OLEDB.12.0;" + #"data source=" + openFileDialog1.FileName;
OleDbCommand cmd = new OleDbCommand();
cn.Open();
DataTable table = cn.GetSchema("Tables");
int i = 0;
foreach (System.Data.DataRow row in table.Rows)
{
if ((string)row["TABLE_TYPE"] == "TABLE")
{
comboBox1.Items.Add(row["TABLE_NAME"]);
Tables[i] = row["TABLE_NAME"].ToString();
listBox1.Items.Add(Tables[i]);
i++;
n++;
}
}
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
OleDbConnection conne = new OleDbConnection();
conne.ConnectionString = #"provider=Microsoft.ACE.OLEDB.12.0;" + #"data source=" + openFileDialog1.FileName;
conne.Open();
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conne;
DataTable Dt = new DataTable();
cmd.CommandText = "select * from " + comboBox1.Text;
OleDbDataAdapter adapter = new OleDbDataAdapter();
adapter.SelectCommand = cmd;
adapter.Fill(Dt);
dataGridView1.DataSource = Dt;
dataGridView1.Visible = true;
conne.Close();
}
private void button2_Click(object sender, EventArgs e)
{
saveFileDialog1.Filter = "accdb|*.accdb";
saveFileDialog1.Title = "Save Access DataBase File";
saveFileDialog1.FileName = strFileName;
saveFileDialog1.ShowDialog();
System.IO.File.Copy(openFileDialog1.FileName, saveFileDialog1.FileName);
ADOX.Catalog cat = new ADOX.Catalog();
cat.Create("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + saveFileDialog1.FileName);
Console.WriteLine("Database Created Successfully");
OleDbConnection connsave = new OleDbConnection();
connsave.ConnectionString = #"provider=Microsoft.ACE.OLEDB.12.0;" + #"data source=" + saveFileDialog1.FileName;
connsave.Open();
OleDbCommand cmdsave = new OleDbCommand();
cmdsave.Connection = connsave;
OleDbConnection connopen = new OleDbConnection();
connopen.ConnectionString = #"provider=Microsoft.ACE.OLEDB.12.0;" + #"data source=" + openFileDialog1.FileName;
connopen.Open();
OleDbCommand cmdopen = new OleDbCommand();
cmdopen.Connection = connopen;
int i = 0;
foreach (string strtablename in Tables)
{
if (i < n)
{
cmdsave.CommandText = "CREATE TABLE [" + Tables[i] + "]";
cmdsave.ExecuteNonQuery();
cmdsave.CommandText = "DELETE FROM [" + Tables[i] + "]";
cmdsave.ExecuteNonQuery();
cmdopen.CommandText = "SELECT * FROM [" + Tables[i] + "]";
cmdopen.ExecuteNonQuery();
cmdsave.CommandText = "INSErT INTO [" + Tables[i] + "]";
cmdsave.ExecuteNonQuery();
i++;
}
}
connopen.Close();
connsave.Close();
textBox2.Text = saveFileDialog1.FileName.ToString();
MessageBox.Show("DataBase Save Sucessfull in \"" + textBox2.Text + "\"");
}

You could execute an INSERT INTO statement using the IN clause:
INSERT INTO DestinationTable (DestinationField)
IN '' [;DATABASE= C:\Users\Rob\Documents\Northwind 2007.accdb]
SELECT SourceField FROM SourceTable
They go into more detail here:
http://blogs.office.com/b/microsoft-access/archive/2009/03/27/accessing-external-data-using-the-in-clause.aspx