使用Winforms从SQL Server 2008r2检索数据

Question

I am creating ac# windows form app, which will retrieve the data from a DB that is already created in sql server2008r2. There are 2 win forms in my app, 1st one is for getting the login details, the 2nd one is for display the data that are relevant to given UserID & Password. I can't get the data to my 2nd form. This is my code:

** * **** 1st form * ** *

 public partial class FormLog_in : Form
 {
    SqlConnection con = new SqlConnection("Data source=CHINTHAK-PC ; Initial Catalog=FlintecTest; Integrated Security = yes;");
    SqlDataAdapter da = new SqlDataAdapter();
    SqlCommand cmd = new SqlCommand();

    public FormLog_in()
    {
        InitializeComponent();
    }

    private void btnLogIn_Click(object sender, EventArgs e)
    {
        if (!(string.IsNullOrEmpty(txtUserName.Text)) && !(string.IsNullOrEmpty(txtPassword.Text)))
        {
            con.Open();
            string query = "SELECT count(*) FROM LogIn  WHERE UesrName=@1 AND PassWord=@2 ";
            cmd = new SqlCommand(query, con);
            cmd.Parameters.Add("@1", SqlDbType.NVarChar).Value = txtUserName.Text;
            cmd.Parameters.Add("@2", SqlDbType.NVarChar).Value = txtPassword.Text;
            int count = Convert.ToInt32(cmd.ExecuteScalar());
            con.Close();

            if (count > 0)
            {
                MessageBox.Show("Valid Username and Password");
                Welcome f1 = new Welcome();
                f1.Show();

            }
            else
                MessageBox.Show("Invalid Username or Password try again");
        }

* **** 2nd form * *

public partial class Welcome : Form
{
    string query = null;

    SqlConnection con = new SqlConnection("Data source=CHINTHAK-PC ; Initial Catalog=FlintecTest; Integrated Security = yes;");
    SqlDataAdapter da = new SqlDataAdapter();
    BindingSource userTable = new BindingSource();
    DataSet ds = new DataSet();

    public Welcome()
    {
        InitializeComponent();

    }

    private void Welcome_Load(object sender, EventArgs e)
    {
        query = "SELECT * FROM  Users WHERE UserName=@x AND Users.Password=@y ";//x should be given username by current login
        da.SelectCommand = new SqlCommand(query, con);                          //y should be given password by current login
        ds.Clear();
        da.Fill(ds, "usr");
        userTable.DataSource = ds.Tables["usr"];

        txtFristName.DataBindings.Add(new Binding("Text", userTable, "FirstName"));
        txtLastName.DataBindings.Add(new Binding("Text", userTable, "LastName"));
        txtAddress.DataBindings.Add(new Binding("Text", userTable, "Address"));
        txtTelephone.DataBindings.Add(new Binding("Text", userTable, "Telephone"));
        txtEmail.DataBindings.Add(new Binding("Text", userTable, "Email"));
        txtFax.DataBindings.Add(new Binding("Text", userTable, "Fax"));
        txtSection.DataBindings.Add(new Binding("Text", userTable, "Section"));
        txtPosition.DataBindings.Add(new Binding("Text", userTable, "Position"));
    }
}

Answer 1

Why not not change your constructor in your welcome form to receive parameters.

 public Welcome(String usr, String pword)
{
    InitializeComponent();
    this.Username=usr;
    this.Password=pword; // you should have a form of encryption for your password
}

So, when you call, you do:

Welcome f1 = new Welcome(txtUsername.Text,txtPassword.Text);

and then you add properties in welcome form like:

private String Username { get; set; }
private String Password { get; set; }

then add the 2 parameters in welcome form load:

cmd.Parameters.Add("@x", SqlDbType.NVarChar).Value = Username;
cmd.Parameters.Add("@y", SqlDbType.NVarChar).Value = Password;

Answer 2

You could use constructors to solve your problem

When you hit the "login" button (supposing that there's one) you could:

private void login_Click(object sender, System.EventArgs e)
{
    Form2 frm=new Form2(userName.text,password.tex);
    frm.Show();
}

Your second form constructor could be:

public Form2(string user, string pass)
{
  InitializeComponent(); 
  //Save your parameters here so you can use them with the query
}

There are other ways to do this. http://www.codeproject.com/Articles/14122/Passing-Data-Between-Forms

Answer 3

Of course you cannot retrieve data from database in second form since you are not

1- you didn't send the x and y parameters to to the second Form

Form2 frm = new Form2(userName.text,password.tex);
frm.Show();

2- must pass x and y to the query in SqlCommand and execute the query

query = "SELECT * FROM  Users WHERE UserName='"+ x +"'AND Password='"+y+"'";

Final code

in Form one

if (count > 0)
{ 
    MessageBox.Show("Valid Username and Password");
    Welcome f1 = new Welcome( txtUserName.Text,txtPassword.Text);
    f1.Show();
}

in Form Two

string x, y;

public Welcome(String usr, String pword)
{
    InitializeComponent();
    x = usr; y = pword;
}

private void Welcome_Load(object sender, EventArgs e)
{
    query = "SELECT * FROM  Users WHERE UserName='"+ x +"'AND Password='"+y+"'";

    cmd.SelectCommand = new SqlCommand(query ,con);

    ds.Clear();
    cmd.Fill(ds);

    userTable.DataSource = ds.Tables[0];

    txtFristName.DataBindings.Add(new Binding("Text", userTable, "FirstName"));
    txtLastName.DataBindings.Add(new Binding("Text", userTable, "LastName"));
    txtAddress.DataBindings.Add(new Binding("Text", userTable, "Address"));
    txtTelephone.DataBindings.Add(new Binding("Text", userTable, "Telephone"));
    txtEmail.DataBindings.Add(new Binding("Text", userTable, "Email"));
    txtFax.DataBindings.Add(new Binding("Text", userTable, "Fax"));
    txtSection.DataBindings.Add(new Binding("Text", userTable, "Section"));
    txtPosition.DataBindings.Add(new Binding("Text", userTable, "Position"));
}