using LINQ update particular column in asp.net mvc 3 - asp.net-mvc-3

Question

I have following code for updating user's column
public void UpdateLastModifiedDate(string username)
{
using (AppEntities db = new AppEntities())
{
var result = from u in db.Users where (u.UserName == username) select u;
if (result.Count() != 0)
{
var dbuser = result.First();
dbuser.LastModifiedDate = DateTime.Now;
db.SaveChanges();
}
}
}
I have other's 2 function of almost same of above function for UpdateLastLogOutDate, UpdateLastLoginDate. So, I decided to define single function for all to update Last Date like:
public void UpdateLastDate(string username, string ColumnName);
Here, I can not put ColumnName variable like this:
dbuser.ColumnName = DateTime.Now;
Is there any other way to do this using LINQ

Answer 1

You could define the method like this:
public void Update(string username, Action<User> action)
{
using (AppEntities db = new AppEntities())
{
var result = from u in db.Users where (u.UserName == username) select u;
if (result.Count() != 0)
{
var dbuser = result.First();
action(dbuser);
db.SaveChanges();
}
}
}
And now there could be different usages of this method:
Update("john", user => user.LastModifiedDate = DateTime.Now);
Update("smith", user => user.UpdateLastLogOutDate = DateTime.Now);
Update("admin", user =>
{
user.LastModifiedDate = DateTime.Now;
user.UpdateLastLogOutDate = DateTime.Now;
});
But if the expression is not known at compile time you may take a look at dynamic LINQ.

Answer 2

You could write your code this way also by sending an instance of your entity as parameter:
public void UpdateLastModifiedDate(Entityclassname ent) //[like if table name is item then Entityclassname should be items etc..]
{
using (AppEntities db = new AppEntities())
{
var result = from u in db.Users where (u.UserName == ent.username) select u;
if (result.Count() != 0)
{
var dbuser = result.First();
dbuser.LastModifiedDate = DateTime.Now;
dbuser.UpdateLastLogOutDate=ent.UpdateLastLogOutDate ;
db.SaveChanges();
}
}
}