Question:
Given:
string metadata.XAxisColumn -- contains a column name (e.g., "Date") string metadata.YAxisColumn -- contains another columnname (e.g., "Close") When I know the names of the columns up front, of course I can do:
var query = from record in myView where record.Date >= startDate && record.Date <= endDate select record.Close However, the column names are not known until runtime. They're in metadata.XAxisColumn and metadata.YAxisColumn.
What is the correct way to construct a query that works like this:
var query = from record in myView where record.[metadata.XAxisColumn] >= startDate && record.[metadata.XAxisColumn] <= endDate select record.[metadata.YAxisColumn]
Solution:1
You use either ESQL/QueryBuilder (built in to EF) or Microsoft Dynamic Query (a.k.a. Dynamic LINQ -- free via VS Code Gallery).
Solution:2
You could derive from the type of 'record' objects, and add a new property:
public class MyRecord : RecordBase { public XAxis { get { switch (metadata.XAxisColumn) { // for example only; this code will not compile because it depends what kind of object RecordBase is :) case X: return this.X; case Y: return this.Y; } } } } Hope that helps!
Solution:3
You could use Dynamic LINQ for those queries
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