Complex Linq Query, building the Where Clause

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Harald SMS - 18 Oct 2007 10:03 GMT

When building a query for the LinkToSql a need to build a where clause that
has both individual values and range selections like this SQL Query:

- WHERE( (IdItem BETWEEN 1 AND 10 OR IdItem = 15 OR IdItem BETWEEN 30 AND
100 OR IdItem = 500... ) AND ( IdMenu BETWEEN 1 AND 5 OR) ...)

How can I write a LINQ statement that makes a efficient query like this?

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Harald SMS

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Harald SMS - 18 Oct 2007 10:13 GMT

The range and individual values are created at runtime and stored in memory,
so it is the dynamic buildiing of this staement that are a bit tricky.

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Harald SMS

> When building a query for the LinkToSql a need to build a where clause that
> has both individual values and range selections like this SQL Query:
[quoted text clipped - 3 lines]
>
> How can I write a LINQ statement that makes a efficient query like this?

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Jon Skeet [C# MVP] - 18 Oct 2007 15:34 GMT

On Oct 18, 10:13 am, Harald SMS <Harald...@discussions.microsoft.com>
wrote:

> The range and individual values are created at runtime and stored in memory,
> so it is the dynamic buildiing of this staement that are a bit tricky.

If you build it up using extension methods directly instead of a query
expression, it's not too bad:

var query = dataContext.WhicheverTable; // The source part

if (restrictByFirstCriterion)
{
query = query.Where(item => item.Foo > wibble);
}
if (restrictBySecondCriterion)
{
query = query.Where(item => item.Bar < 0);
}
etc

Basically keep applying Where clauses (or others, such as joins) as
appropriate.

Jon

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Complex Linq Query, building the Where Clause

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