c# - type arguments can't be inferred from the usage for higher-order function -

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i have following higher-order function:

public static func<t, bool> not<t>(func<t, bool> otherfunc) {     return arg => !otherfunc(arg); }

and trying call that:

var isvalidstr = linqutils.not(string.isnullorwhitespace);

compiler gives me "type arguments cannot inferred usage" error. following works:

var isvalidstr = linqutils.not((string s) => string.isnullorwhitespace(s));

i wonder difference is? string.isnullorwhitespace non-overloaded function same signature.

as mentioned in comments, following works , still doesn't explain why type inference fails in case:

var isvalidstr = linqutils.not<string>(string.isnullorwhitespace);

the details of issue dealing answered eric lippert on blog, here.

basically, "david b" said in comments, "isnullorwhitespace method group. method group has 1 participating member today, more in future."


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