SQL Insert Query Using C#

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);
        }
    }