I'm very new to Entity, and I'm trying to find all elements in a DbSet object that match a boolean condition that's passed as a string:
Example:
string condition = "Weight > 30 && Age == 20";
var results = context.Data.FindIf(condition);
where Weight and Age are properties of Data, and the boolean condition given can vary. I can hard code it easily with LINQ expressions but is there a way to do it in the way I described?
Expression trees can do want you want here. You can parse the string to build the expression tree.
You could use a raw SQL query and just execute normal SQL against it?
context.Database.SqlQuery<Data>("SELECT * FROM [DataTable] WHERE Weight > 30 AND Age = 20");
You can use the DynamicLinqQuery library to use string epxressions against the IQueryable sources. The library is built on top of feature described in MSDN article of Expression tree and dynamic query builders shared by @tdbeckett
It allows you to write dynamic conditions as string e.g.
using System.Linq.Dynamic;
var query =
db.Customers.
Where("City = @0 and Orders.Count >= @1", "London", 10);
There's a Nuget package available for this:
Install-Package DynamicQuery
One you finish installation you can find an HTML file added in the project for help documentation.
var results = db.Data.Where(queryRequest); where queryRequest is a string containing a boolean expression.