Can we delete clauses from linq expression?

I was wondering whether it's possible 开发者_运维技巧to add/remove a where clause from a linq expression/ query operators.

Eg :-

var qry = from e in emp where(e => e.salary > 5000) select e;

Is it possible to remove where expression at a later stage?

Thanks in advance :)

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Yes, it is possible, but you need to implement an ExpressionVisitor class to evaluate the composite expression and change it according to your needs. Unless you are doing something relatively complex there is probably a better way to accomplish what you want.

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you can only adjust your filtering as far as i know

for example if are trying to delete based on condition e.salary > 5000 , they you should try something like

var diffQry = from e in emp where(e => e.salary <= 5000) select e;

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If you want to programmatically add and remove where clauses you can use query operators.

var query = emp.Select(x => x);

if (someCondition)
  query = query.Where(x => x.Price > 50);

You need to expand on your question a little more.

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If qry is an IQueryable<T> -- for example, a LINQ-to-SQL or LINQ-to-Entities query -- then it should be possible to analyse the underlying expression tree and build a new one excluding the Where clause.

If qry is a plain IEnumerable<T> -- for example, a LINQ-to-Objects query -- then this can't be done since there will be no expression tree to analyse.

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I think WHERE clause is required if there is a conditional query. Otherwise (if no condition) you can use:

var qry = from e in emp select e;