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POUnexpected type compilation issue when using pipe operations in F#
 

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  1. POUnexpected type compilation issue when using pipe operations in F#
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    <p>I am trying to parse a directory of XML files and then select the value of particular attribute if a given node is present. Am not able to understand the reason for the compilation error that the following F# is causing.</p> <pre><code>open System open System.IO open System.Xml open System.Xml.XPath open System.Xml.Linq let configRootDirectory = @"C:\dir" let relativeProductDir = @"relDir" let ExtractConfiguredCalculator (productConfigFile:string) = let xmlNavigator = XPathDocument(productConfigFile).CreateNavigator() let node = xmlNavigator.SelectSingleNode(@"Product/SupportedRisk/Risk[@type='PV']") node.GetAttribute("methodology", "") let configFile = Directory.GetFiles(Path.Combine(configRootDirectory, relativeProductDir), @"*.xml") |&gt; Seq.cast&lt;string&gt; |&gt; Seq.iter(fun configFileName -&gt; ExtractConfiguredCalculator(configFileName)) |&gt; Seq.filter(fun configuredCalculatorNode -&gt; configuredCalculatorNode != null) |&gt; Seq.iter(fun calculator -&gt; Console.WriteLine(calculator)) </code></pre> <p>The above snippet is from the code that I am experimenting with in LinqPad. The error message seen is as below.</p> <pre><code>This expression was expected to have type unit but here has type string </code></pre> <p><strong>Update</strong> Trying to get more f#-ish. Please suggest if something can be improved.</p> <pre><code>let configFile = Directory.GetFiles(Path.Combine(configRootDirectory, relativeProductDir), @"*.xml") |&gt; Seq.map(fun configFileName -&gt; let xmlNavigator = XPathDocument(configFileName).CreateNavigator() let node = xmlNavigator.SelectSingleNode(@"Product/SupportedRisk/Risk[@type='PV']") match node with | null -&gt; "PV not configured" | _ -&gt; let attributeValue = node.GetAttribute("methodology", "") match attributeValue with | null -&gt; "Calculator not configured" | _ -&gt; attributeValue) |&gt; Seq.iter (printfn "%s") </code></pre>
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    1. COCan you post the error message?
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    2. COOops! missed that! Error message as below:This expression was expected to have type unit but here has type string
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