Conditional Multiple Fields Searching and Filtering in LINQ

Question

Assuming that we have the following table:

Person:
  PersonID,
  Name,
  Age,
  Gender

And we are providing a search function that allows u

Answer 1

Try code like this

       string personName = txtPersonName.Text;
       int personAge = Convert.ToInt32(txtAge.Text);
       var opportunites =  from p in this.DataContext.Persons
                            select new
                            {
                                p.PersonID,
                                p.Name,
                                p.Age,
                                p.Gender
                            };

        if (personsID != 0)
            opportunites = opportunites.Where(p => p.PersonID == personID);

        if (personName != string.Empty)
            opportunites = opportunites.Where(p => p.Name.StartsWith(personName));

        if (personAge != 0)
            opportunites = opportunites.Where(p => p.Age == personAge);

This will work fine. If personName is not given it will be not add to where, and if given then it will added.

Answer 2

One alternative which I have used in SQL which could be implemented in Linq too is

var p = from p in Person
       where p.Name == Name_TextBox || Name_TextBox == String.Empty
       select p;

(Note that your 'linq' is using SQL syntax, which won't compile. Also you can't declare a var as you are doing without directly assigning a value)

Answer 3

why not use the null coalescing operator? eg.

var products = from a in context.products where a.ID == (productID ?? a.ID) select a;

This works really well on my system