CODEWITHSUNDEEP
c#linqentity-frameworkentity-framework-5
Matt
Matt

Reputation: 26981

Programmatically building a query with LINQ statement with entity framework

Let's say I have a query like:

r = r.Where(x => iEnumerableMachineNames.Contains(x.Machine.Name) 
                 || x.Server==true);

Is there a way to build the predicate (I think that's what it's called) outside of the statement, for instance

t = (x => iEnumerableMachineNames.Contains(x.Machine.Name));
s = (x => x.Server==true)
q = t.Or(s);
r = r.Where(x => q);

Basically I want to programmatically build my query based on input parameters, for EF 5.

Upvotes: 4

Views: 102

Answers (1)

Moho
Moho

Reputation: 16543

You can build expressions dynamically but not as simply as your pseudo code - it requires reflection and expression trees (read this).

A simple way to accomplish what it seems like you'd like to do is to short circuit different parts of the predicate using boolean flags:

bool testMachineName;
bool testIsServer;

r = r.Where( x =>
    ( !testMachineName || iEnumerableMachineNames.Contains( x.Machine.Name ) ) ||
    ( !testIsServer || x.Server ) );

Upvotes: 1

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