- Edited examples based on Bart's feedback (see comments).
This post is meant for developers who are upgrading legacy webapplications to .NET 3.5 and for developers who know Linq, but have a hard time finding scenarios to apply Linq.
I got my inspiration for this post by reading Professional Refactoring in C# & ASP.NET (Wrox Programmer to Programmer)
.I downloaded the My Web Pages Starter Kit to find some examples, which is written for .NET 2.0. I upgraded it to .NET 3.5 to use Linq.
Below you can find some real-world examples of refactoring to use Linq.
Querying collections never has been this clean!
Example one
Before
1: bool blnTravelDiary = false;
2: foreach (string theme in themes) {
3: if (Path.GetFileName(theme) == "TravelDiary")
4: blnTravelDiary = true;
5: }After
1: bool blnTravelDiary = themes.Any(theme => Path.GetFileName(theme) == "TravelDiary");
Example two
Before
1: foreach (RoleData data in _roles) {
2: if (data.RoleName.Equals(roleName, StringComparison.CurrentCulture))
3: return true;
4: }5: return false;
After
1: bool exists = _roles.Any(roleData => roleData.RoleName.Equals(roleName, StringComparison.CurrentCulture));
Example three
Before
1: foreach (RoleData data in _roles) {
2: if (data.RoleName == rolename) {
3: found = data;4: break;
5: } 6: }7: return found;
After
1: var found = from RoleData data in _roles
2: where data.RoleName == rolename
3: select data;4: return found.FirstOrDefault();
Example four
Before
1: List<string> foundRoles = new List<string>();
2: foreach (RoleData data in _roles){
3: if (data.Users.Contains(username))
4: foundRoles.Add(data.RoleName); 5: }6: return foundRoles.ToArray();
After
1: var data = from RoleData roleData in _roles
2: where roleData.Users.Contains(username)
3: select roleData.RoleName;4: return data.ToArray();
Example five
Before
1: foreach (MembershipUser user in Membership.GetAllUsers())
2: {3: if (string.Compare(user.UserName, txtUserName.Text, true) == 0)
4: { 5: Login1.UserName = user.UserName;6: return;
7: } 8: }After
1: var matchingUsers = from MembershipUser user in Membership.GetAllUsers()
2: where string.Compare(user.UserName, txtUserName.Text, true) == 0
3: select user.UserName; 4: 5: var firstMatch = matchingUsers.FirstOrDefault(); 6: 7: if (firstMatch != null) {
8: Login1.UserName = firstMatch; 9: }
