Question

I am a newbie with c# and window form

I am doing a web service, and use a form which contain a datagridview, but am having quite a lot of problems.

How do I validate user input with a database, for example, when the user inserts a username, however the username already exists in the database, I should prompt the user to enter another username.

I tried before in previous thread that I validate that particular column with only user can enter 0 or 1….

how to validate particular column cell field when editing
Is it something similar?

Do I need a web method for this?

p.s basically what I want is to have a textbox field in a window form, in which the user will key in a username to add it to the database, however, when they click on the add button, if the user name already exists, there will be a prompt. If not it will add it to database using the insert web method.

The data is retrieve by web method… meaning that I have to use a web method to help me with this check right…but how?

my code for web method

[WebMethod]  
public DataSet validateUserName()  
{   

    SqlConnection conn = 
        new SqlConnection("Data Source=.\\SQLEXPRESS;
            Initial Catalog=User;Integrated Security=True");   
    SqlCommand dbCommand = new SqlCommand();  
    dbCommand.CommandText = 
        @"SELECT COUNT(*) 
        FROM User 
        WHERE UserName=@UserName"; 
    // this textusername is from the window form  
    dbCommand.Connection = conn;  
    SqlDataAdapter da;   
    da = new SqlDataAdapter();   
    da.SelectCommand = dbCommand;

    DataSet ds = new DataSet();  
    da.Fill(ds);   
    return ds;

}

this is my window form code

private void btnAdd_Click(object sender, EventArgs e)

{
    WSBrandData validate = new WSBRandData();
    if (validate.validateUserName(txtUserName.Text))
    {
        MessageBox.Show("UserName is allocated");
        txtUserName.Text = "";
    }
    else
    {
       WSBrandData add = new WSBRandData();

        String[] names = null;

        names = Convert.ToString(DGVBrand.CurrentRow.Cells[1].Value).Split(';');
        String tagg = txtUserName.Text + ";";
        names[1] = tagg;

        DGVBrand.DataSource = add.addUserName(Convert.ToInt32(DGVBrand.CurrentRow.Cells[0].Value), names[0], names[1], Convert.ToInt32(DGVBrand.CurrentRow.Cells[3].Value));
        BindBrand();

    }




}

Answer 1

Start here :

[WebMethod]  
public Boolean UserNameExists(String userName)  
{   

    SqlConnection conn = 
        new SqlConnection("Data Source=.\\SQLEXPRESS;
            Initial Catalog=User;Integrated Security=True");   
    SqlCommand dbCommand = new SqlCommand();  
    dbCommand.CommandText = 
        @"SELECT COUNT(*) 
        FROM User 
        WHERE UserName='" + userName + "'";
    // this textusername is from the window form  
    dbCommand.Connection = conn;  

    conn.Open();

    int matchesCount = int.Parse(dbCommand.ExecuteScalar().ToString());

    conn.Close();  

    return matchesCount != 0;

}

In your forms application:

if (webReference.Type.UserNameExists(this.userNameTextBox.Text) )
{
    // Do something
}
else
{
    // Do something else
}