How to create a QueryExpresion from LambdaExpression

I am creating a dynamic query based on some user input

For this I am creating a QueryExpression that is constructed at the runtime.

For part of the my query one of the filter is available to me in the form of LambdaExpression, as I am using the Dynamic LINQ API for resolve the filter condition from the string based expression. So I have something like below:

string expr = "Cost > 200";

QueryExpression qe = null;

// Adding some pre-prepared Query expressions to the main expressions

qe &= someAdditionalFilter;

Expression<Func<Employee, bool>> es = DynamicExpression.ParseLambda<Employee, bool>(expr);

I want to do something like below:

qe &= es;

Now the issue is having a Lambda expression at hand how do I convert it to the QueryExpression so that i can do something like:

qe &= LambdaExpressionToQueryExpression(es);

AFAIK Lightspeed engine converts all the LINQ based syntax into their native API like QueryExpression and Query before execution.

But I donot know how and what methods to call in order to achieve this. Any suggestions or solutions will be deeply appreciated as this is holding my work.

~ Sidharth

You're correct that the LightSpeed engine converts LINQ expressions into core API QueryExpression and Query objects in order to execute them.  However, the conversion engine isn't exposed: it's internal to the LINQ provider.  There's not really a way to combine LINQ expressions with QueryExpressions.

Your best solution is therefore to build your whole query as a LINQ expression.  That is, instead of writing qe &= LambdaExpressionToQueryExpression(es), write something like:

var andedExpression = Expression.AndAlso(existingLinqQuery, es);

and pass the andedExpression to a LINQ Where clause.

Hi Ivan,

Well when I began on building this dynamic query, I initially started with LINQ expressions only.

But in my scenario, I have to support multiple subqueries inside the where clause. Which, when i tried doing it with LINQ, I got stuck due to the limited support of LINQ based expressions.

Earlier, I posted another question on the thread http://www.mindscape.co.nz/forums/Thread.aspx?ThreadID=2070

with an issue, which was relatively a minor problem but a big hurdle for continue using LINQ.

Thus, I then resorted to the Base Lightspeed APIs. Is there a possibility you can expose some utility methods for converting the LambdaExpression to QueryExpression? Any more thoughts on how can I proceed.

~ Sidharth