How to embed string condition in linq query

I want to ap开发者_JAVA技巧ply few conditions in my linq query. My scenario is I am fetching records from a table and if user select some criteria then apply condition according to. So what i want to do is

var linq = from p in Post select p
//now if user apply that condition
string id = "1"; //Here 1 is what user inputs
string condition = where p.id == id 
//then it executes query like this 
linq = from p in Post condition select p

Can i do this in linq if yes then how

var linq = from p in Post select p;

//now if user apply that condition
string id = "1"; //Here 1 is what user inputs

if (!String.IsNullOrEmpty(id))
{
    linq = linq.Where(p => p.id == id);
}

return linq.ToList(); // or whatever you want to do with it at this point

You will probably want to look into dynamic linq or depending on how complex you want to make the condition use expression trees

You might want to try:

string id = "1";
string condition = "p.id == " + id;
var linq = from p in Post 
           where (condition) 
           select p;

or with a lambda:

string id = "1";
string condition = "p => p.id == " + id;
var linq = Post.Where(condition).SingleOrDefault();

See the following:

Scott Gu's post on Dynamic Linq

Querying Entity with LINQ using Dyanmic Field Name

Basics of Linq Expression Trees