LINQ Substring CRM 2011 - linq

Question

I have a LINQ query that pulls down some information based on certain criteria in the Where clause from CRM 2011. But I want to add it so it only looks at the first 5 characters of the Zip instead of the whole Zip. I tried adding SubString. But if the value is null it will fail. How would you go about matching the first 5 characters of the Zip in the Where clause. This is my query.
var lQuery = (from a in gServiceContext.CreateQuery("account")
where (a["name"].Equals(lLead.AccountName) &&
a["address1_postalcode"].Equals(lLead.ZipCode) &&
a["address1_stateorprovince"].Equals(lLead.State)) ||
(a["address1_line1"].Equals(lLead.Address1) &&
a["address1_postalcode"].Equals(lLead.ZipCode) &&
a["address1_city"].Equals(lLead.City))
select new
{
Name = !a.Contains("name") ? string.Empty : a["name"],
City = !a.Contains("address1_city") ? string.Empty : a["address1_city"],
State = !a.Contains("address1_stateorprovince") ? string.Empty : a["address1_stateorprovince"],
Zip = !a.Contains("address1_postalcode") ? string.Empty : a["address1_postalcode"],
AccountId = !a.Contains("accountid") ? string.Empty : a["accountid"]
})
Thanks!

Answer 1

One of the other issues with String.Substring is that it throws if the string isn't long enough, i.e. you try to get the first 5 characters of a 4 character string. You can use a simple helper method like this:
where First(a["address1_postalcode"], 5) == lLead.ZipCode
(You might need to convert or cast a["address1_postalcode"] to string depending on what type it returns.)
public static string First(string s, int charcount)
{
if (s == null) return String.Empty;
return s.Substring(0, Math.Min(s.Length, charcount));
}