ASP.Net Server从DB打印数据但不会写入DB

Question

我遇到了连接字符串或类似问题。因为数据是从DB打印的，但不会使用INSERT查询字符串写入DB。

这是.cs代码部分：

    protected void Page_Load(object sender, EventArgs e)
{
    Load_Data();
}

protected void Load_Data()
{
    DataTable dtUsers = new DataTable();

    // connect to sql
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["dbcs"].ConnectionString);

    // create sql
    string sql = "SELECT Username, Fullname, Email FROM Users;";

    // command
    SqlCommand cmd = new SqlCommand(sql, con);

    // load data to dt
    con.Open();

    SqlDataReader reader = cmd.ExecuteReader();
    dtUsers.Load(reader);

    con.Close();

    // print data to gridview
    GridView1.DataSource = dtUsers;
    GridView1.DataBind();
}

protected void Button1_Click(object sender, EventArgs e)
{
    // connect to sql
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["dbcs"].ConnectionString);

    // create query
    string sql = "INSERT INTO Users (UserName,Passowrd,Email,FullName) VALUES ('" + txtUsername.Text + "','"+ txtPwd.Text + "','"+ txtEmail.Text + "','" + txtFullName.Text + "');";

    // command
    SqlCommand cmd = new SqlCommand(sql, con);

    // save data to db
    con.Open();
    cmd.ExecuteNonQuery();
    con.Close();
}

谢谢你！