Need certain LINQ command using let

I want to transform a foreach loop into LINQ. The code looks like this:

foreach (XmlNode localNode in localXmlNodeList)
{
    var localKeyNode = localNode.SelectSingleNode(inputKeyName);
    var localValueNode = localNode.SelectSingleNode(inputValueName);

    if ((localKeyNode == null) || (localValueNode == null))
        continue;

    localReturn.Add(localKeyNode.InnerText, localValueNode.InnerText);
}

I wanted to use something like:

from X in Y
let varA = Y.A
let varB = Y.B
where method(varA, varB)
select varA, varB;

but I always end up using a foreach loop like:

foreach(var X in Y.Where(varA => something(varA.subA.microSubA, varB.subB.microSubB)))
{
    somethingAgain(varA.subA.microSubA, varB.subB.microSubB)
}

where I wasn't able to introduce "let".

Can Somebody help me ?

Jon Skeet
people
quotationmark

You can use let in a foreach loop:

// Query modified slightly to make more sense...
foreach (var X in from X in Y
                  let varA = X.A
                  let varB = X.B
                  where method(varA, varB)
                  select new { varA, varB })

It's ugly, but it should still work - it's just an expression.

Or, better IMO, declare a separate query variable first:

var query = from X in Y
            let varA = X.A
            let varB = X.B
            where method(varA, varB)
            select new { varA, varB };
foreach (var X in query)
{
    ...
}

Of course, let really just corresponds to another Select to introduce the range variable - so you can express it in dot notation as well:

var query = Y.Select(X => new { X, varA = X.VarA })
             .Select(p => new { p.X, p.varA, varB = p.X.VarB })
             .Where(p => method(p.varA, p.varB))
             .Select(p => new { p.varA, p.varB });

people

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