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Check if table exists using command

I'm trying to write a method to check if a table exists. I am trying to use the using statement to keep it consistent through my database.
public void checkTableExists()
{
connectionString = #"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\keith_000\Documents\ZuriRubberDressDB.mdf;Integrated Security=True;Connect Timeout=30";
string tblnm = "BasicHours";
string str = "SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = " + tblnm + ");";
SqlDataReader myReader = null;
int count = 0;
try
{
using (SqlConnection connection = new SqlConnection(connectionString))
{
using (SqlCommand command = new SqlCommand(str, connection))
{
connection.Open();
using (SqlDataReader reader = command.ExecuteReader())
{
MessageBox.Show("The count is " + count);
myReader = command.ExecuteReader();
while (myReader.Read())
{
count++;
}
myReader.Close();
MessageBox.Show("Table Exists!");
MessageBox.Show("The count is " + count);
}
connection.Close();
}
}
}
catch (SqlException ex)
{
MessageBox.Show("Sql issue");
}
catch (Exception ex)
{
MessageBox.Show("Major issue");
}
if (count > 0)
{
MessageBox.Show("Table exists");
}
else
{
MessageBox.Show("Table doesn't exists");
}
}
It throws an exception when it hits the try block. It catches in the SqlException block.
This is the point where I am learning to interact with databases again. The solution would be good, but more importantly, a brief explanation of where I have need to learn how to improve my code.
Thanks
Keith

Your code fails because when you write directly a query searching for a string value then this value should be enclosed in single quotes like 'BasicHours'.
However there are some improvements to apply to your actual code.
First, you can use a simplified sql command.
Second, you use parameters instead of string concatenations.
SqlCommand cmd = new SqlCommand(#"IF EXISTS(
SELECT 1 FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = #table)
SELECT 1 ELSE SELECT 0", connection);
cmd.Parameters.Add("#table", SqlDbType.NVarChar).Value = tblName;
int exists = (int)cmd.ExecuteScalar();
if(exists == 1)
// Table exists
This command text don't require you to use an SqlDataReader because the query returns just one row with one 'column' and the value of this single cell is either 1 or 0.
A lot less overhead.
A part from this, it is of uttermost importance, that you never build sql queries concatenating strings. This method is well know to cause problems.
The worse is called SQL Injection and could potentially destroy your database or reveal confidential information to hackers. The minor ones are crashes when the string concatenated contains single quotes. Use always a parameterized query.

I have used the following code in my project and worked for me:
try
{
using (con = new SqlConnection(Constr);)
{
con.Open();
string query = $"IF EXISTS (SELECT * FROM sys.tables WHERE name = '{tableName}') SELECT 1 ELSE Select 0;"
Exists = int.Parse(sqlQuery.ExecuteScalar().ToString())==1;
con.Close();
}
}
catch{}

The problem could be the line: string tblnm = "BasicHours";. You table name is a string and should be apostrophed, try this: string tblnm = "'BasicHours'";
Inside catch blocks you could also log exception messages and details.

Thanks for the help on this issue. This is the solution that I'm implemnenting.
public void checkTableExists()
{
connectionString = #"
Data Source=(LocalDB)\MSSQLLocalDB;
AttachDbFilename=C:\Users\keith_000\Documents\ZuriRubberDressDB.mdf;
Integrated Security=True;
Connect Timeout=30";
string tblName = #"BasicHours";
string str = #"IF EXISTS(
SELECT 1 FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = #table)
SELECT 1 ELSE SELECT 0";
try
{
using (SqlConnection connection = new SqlConnection(connectionString))
{
using (SqlCommand command = new SqlCommand(str, connection))
{
connection.Open();
SqlCommand cmd = new SqlCommand(str, connection);
cmd.Parameters.Add("#table", SqlDbType.NVarChar).Value = tblName;
int exists = (int)cmd.ExecuteScalar();
if (exists == 1)
{
MessageBox.Show("Table exists");
}
else
{
MessageBox.Show("Table doesn't exists");
}
connection.Close();
}
}
}
catch (SqlException ex)
{
MessageBox.Show("Sql issue");
}
catch (Exception ex)
{
MessageBox.Show("Major issue");
}
}

Insert Data Into Databse Once User Clicks on Button

I am trying to write a code that will insert data into a database once user click on button. There's something wrong with the code and it does not seem to work properly. I connect to an external database based on my hosting provider.
private void druk_Click(object sender, EventArgs e)
{
MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;
myConnectionString = "server=s59.hekko.net.pl;uid=truex2_kuba;" +
"pwd=test;database=truex2_kuba;";
try
{
conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString);
conn.Open();
MySqlCommand cmd = new MySqlCommand();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
MessageBox.Show(ex.Message);
}
cmd.CommandText = "insert into [barcode]values(#class, #tree, #type, #amount, #length, #width, #square)";
cmd.Parameters.AddWithValue("#class", klasa.Text);
cmd.Parameters.AddWithValue("#tree", gatunek.Text);
cmd.Parameters.AddWithValue("#type", rodzaj.Text);
cmd.Parameters.AddWithValue("#amount", amount.Text);
cmd.Parameters.AddWithValue("#length", length.Text);
cmd.Parameters.AddWithValue("#width", width.Text);
cmd.Parameters.AddWithValue("#square", textBox1.Text);
int a = cmd.ExecuteNonQuery();
if (a > 0)
{
MessageBox.Show("Zapisane do raportu");
}

The issue is this:
MySqlCommand cmd = new MySqlCommand();
is in the scope of the try, catch block.
Further on in the code, there was a reference to the cmd variable which is null and hence no data goes in.
Move it outside of the try, catch block.

Insert data into local database using ado.net in a console application

Here is what I have written so far.There is no exception so I am assuming the connection is working fine but no data is inserted into the database table. Please tell me what is wrong with my code
SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MyETL.Properties.Settings.connectionStr"].ConnectionString);
try
{
conn.Open();
// foreach (student stu in stulist)
// {
string strQuery = "INSERT INTO Student(Sid,st_name) VALUES (#id,#name)";
SqlCommand cmd = new SqlCommand(strQuery, conn);
cmd.Connection = conn;
cmd.Parameters.AddWithValue("#id", "111");
cmd.Parameters.AddWithValue("#name", "nallia");
cmd.ExecuteNonQuery();
}
catch
{
conn.Close();
}

Try this
static void Insert()
{
try
{
string connectionString =System.Configuration.ConfigurationManager.ConnectionStrings["MyETL.Properties.Settings.connectionStr"].ConnectionString;
using (SqlConnection conn =new SqlConnection(connectionString))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("INSERT INTO Student(Sid,st_name) VALUES (" +
"#id,#name)", conn))
{
cmd.Parameters.AddWithValue("#Id", 111);
cmd.Parameters.AddWithValue("#Name", "nallia");
int rows = cmd.ExecuteNonQuery();
//rows number of record got inserted
}
}
}
catch (SqlException ex)
{
//Log exception
//Display Error message
}
}

It has been nearly 2,5 years but if you haven't still solved this problem, you should change the "copy to output directory" attribute to "copy if newer". Your database is changing but every time you start debugging, you read the initial version of database so, you see that there is no changes.

Cannot insert the data into the table C# visual studio 2013

i want to write data into a local database table.
When i run the code there are no erros and when i count the rows after the insert statement the message box shows me that a row was inserted.
But when i close the programm and look in my database there are no new rows.
I'm using C# and Visual Studio 2013.
Do anybody know what the problem is?
Thank you.
String connection = "Data Source=(LocalDB)\\v11.0;AttachDbFilename=|DataDirectory|\\Datenbank.mdf;Integrated Security=True;Connect Timeout=30";
SqlConnection cnn = new SqlConnection(connection);
cnn.Open();
String query = "INSERT INTO Customer (ID, Name) VALUES (#id, #name)";
SqlCommand command = new SqlCommand(query, cnn);
command.Parameters.AddWithValue("#id", 1);
command.Parameters.AddWithValue("#name", 'John');
SqlDataReader reader;
command.ExecuteNonQuery();
query = "Select count(ID) from Customer";
command = new SqlCommand(query, cnn);
reader = command.ExecuteReader();
while (reader.Read())
{
MessageBox.Show(reader[0].ToString());
}
reader.Close();

Try like this:
try {
int rowsAffected = command.ExecuteNonQuery();
if (0 < rowsAffected)
MessageBox.Show("Success!");
else
MessageBox.Show("Failed!");
} catch (SqlException ex) {
MessageBox.Show(ex.Message);
} finally {
if (cnn.State == ConnectionState.Open)
cnn.Close();
}
Also refer: Why saving changes to a database fails?

Works perfectly except changes are not saved to the SQL database

Changes are not saved to the SQL database
Why would I want to use '#' in the sql statement instead of the way that I have the statement?
Code:
private void button_Save_Customer_Click(object sender, EventArgs e)
{
sqlString = Properties.Settings.Default.ConnectionString;
SqlConnection sqlConnection = new SqlConnection(sqlString);
try
{
string customer_Ship_ID = customer_Ship_IDTextBox.ToString();
string customer_Ship_Address = customer_Ship_AddressTextBox.Text;
SQL = "UPDATE Customer_Ship SET Customer_Ship_Address = customer_Ship_Address WHERE Customer_Ship_ID = customer_Ship_ID";
SqlCommand sqlCommand = new SqlCommand(SQL, sqlConnection);
sqlCommand.Parameters.AddWithValue("Customer_Ship_ID", customer_Ship_ID);
sqlCommand.Parameters.AddWithValue("Customer_Ship_Address", customer_Ship_Address);
sqlCommand.CommandText = SQL;
sqlConnection.Open();
sqlCommand.ExecuteNonQuery();
sqlConnection.Close();
MessageBox.Show("Record Updated");
}
catch (Exception err)
{
MessageBox.Show(err.Message);
}

Here you can check the MSDN reference for the update command.
Use parameters, Why?
Also check that you need to open and close the connection object, not the command.
In case you want to update the rows with the Customer_ID = "something" you could do like this:
The code (updated after your changes):
private void button_Save_Customer_Click(object sender, EventArgs e)
{
string sqlString = Properties.Settings.Default.ConnectionString;
SqlConnection sqlConnection = new SqlConnection(sqlString);
try
{
int customer_Ship_ID;
if(int.TryParse(customer_Ship_IDTextBox.Text, out customer_Ship_ID))
{
string customer_Ship_Address = customer_Ship_AddressTextBox.Text;
// Customer_Ship: Database's table
// Customer_Ship_Address, Customer_Ship_ID: fields of your table in database
// #Customer_Ship_Address, #Customer_Ship_ID: parameters of the sqlcommand
// customer_Ship_ID, customer_Ship_Address: values of the parameters
string SQL = "UPDATE Customer_Ship SET Customer_Ship_Address = #Customer_Ship_Address WHERE Customer_Ship_ID = #Customer_Ship_ID";
SqlCommand sqlCommand = new SqlCommand(SQL, sqlConnection);
sqlCommand.Parameters.AddWithValue("Customer_Ship_ID", customer_Ship_ID);
sqlCommand.Parameters.AddWithValue("Customer_Ship_Address", customer_Ship_Address);
sqlCommand.CommandText = SQL;
sqlConnection.Open();
sqlCommand.ExecuteNonQuery();
sqlConnection.Close();
MessageBox.Show("Record Updated");
}
else
{
// The id of the textbox is not an integer...
}
}
catch (Exception err)
{
MessageBox.Show(err.Message);
}
}

Seems like your syntax isn't correct. Here's the syntax for the Update:
UPDATE table_name
SET column1=value1,column2=value2,...
WHERE some_column=some_value;
So, Update, what to set, and WHERE to set (which you seem to be missing).
For more, have a look here.

Check your update query
Change it like
string SQL = string.format("UPDATE Customer_Ship SET Customer_Ship_Address='{0}'",putUrVaue);