Question

I have query in link to SQL like this

var password = (from userAccounts in myDb.Physicians
                            where userAccounts.Phy_UserName == txtUserName.Text
                            select userAccounts).FirstOrDefault();

I want to select a specific column with that query, I want to retrieve the row value of userAccounts.Password, userAccounts.Phy_FName, userAccounts.Phy_Password and so on.

is password.Phy_FName allowed? assuming that we have a result? how do I select a value?

Answer 1

You’ve got it right. your Phy_UserName needs to be a column in your database. It’s returning a Physicians object and you can get each value as follows.

// `var physician` is the same as `Physician physician` 
// where you're declaring a Physician object from your DBML file

// we're using `p` for `physician` in the lambda select function
var physician = (from p in myDb.Physicians
                 where p.Phy_UserName == txtUserName.Text
                 select p).FirstOrDefault();

// now that you've got a `physician` object, you can use the properties
// within the object as follows..
var password = physician.Password;
var firstName = physician.Phy_FName;
// etc

// please note that the physician object you have currently has ALL of the 
// database fields for that particular physician

now if you choose to only select your needed properties, you will approach it a little differently.

// first you declare a poco to store only the needed properties.

public class PhysicianViewModel {
    public string Password {get; set;}
    public string FirstName {get; set;}
}

// then you run your select query and drill down to grab
// only the required data fields from the database
var physicianViewModel = (from p in myDb.Physicians
                          where userAccounts.Phy_UserName == txtUserName.Text
                          select new PhysicianViewModel { 
                              Password = p.Password,
                              FirstName = p.Phy_FName }).FirstOrDefault();

// and using them is the same as the above example
// the only difference here is that the `physicianViewModel` doesn't 
// contain ANY properties other than the ones you specified.
var password = physicianViewModel.Password;
var firstName = physicianViewModel.FirstName;

---

Edit

As per your comment below, this is a little aside pertaining to preventing a null value being inserted into a string (nvarchar) field in the database.

The easiest way to do this is to add the required attribute to the property and ensure you’re validating it before submitting it.

public class Physician {
    [Required]
    public string Password {get; set;}
    public string Phy_FName {get; set;}
    public string Phy_LName {get; set;}
}

If you set the allow null to false in the database, and then update your DBML file to reflect the changes, then the [required] attribute will be added to the property automatically.