Clash Royale CLAN TAG#URR8PPP

Linq average of dynamic double

I have a dynamic result set, which contains a key value double (but the compiler still sees it as a dynamic). I am trying to take a cumulative average of this, but cannot figure out the correct cast or how to call the specific overload of the Linq Average() method. It consistently tries to call the Average<dynamic>(Func<dynamic, int> selector) version, when I am pretty sure I need the Average<dynamic>(Func<dynamic, double> selector) version.

Average()

Average<dynamic>(Func<dynamic, int> selector)

Average<dynamic>(Func<dynamic, double> selector)

Intellisense on the Average() and Sum() methods is what is showing me that the compiler is choosing the <dynamic, int> version. How can I specify to use the double version?

Average()

Sum()

<dynamic, int>

double

Here is a good sample of the iterations of things I have tried and their corresponding error. At this point, I feel I have tried every combination, and with or without Cast<double>() and Convert.ToDouble() that I can think of.

Cast<double>()

Convert.ToDouble()

// ## filled with values from DB query, but here with examples ##
var result = new List<dynamic>() new myDouble = 0.123 , new myDouble = 0.456 ;
var cumulativeAvg = new List<double>();


UPDATE My result set turned out to have a hidden null value, which caused the errors:

null

var result = new List<dynamic>()
new myDouble = 0.123
, new myDouble = 0.456
, new myDouble = null
;


For all of the following loops, the ERROR is:
Cannot implicitly convert type 'double' to 'int'

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Average(r => Convert.ToDouble(r.myDouble)));

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Select(r => Convert.ToDouble(r.myDouble)).Average());

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Select(r => Convert.ToDouble(r.myDouble)).ToList().Average());

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Sum(r => Convert.ToDouble(r.myDouble)) / (i + 1));


For all of the following loops, the ERROR is:
Specified cast is not valid.

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Select(r => Convert.ToDouble(r.myDouble)).Cast<double>().Average());

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Cast<double>().Select(r => Convert.ToDouble(r.myDouble)).Average());

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Select(r => Convert.ToDouble(r.myDouble)).Cast<double>().Take(i + 1).Average());


result

results

results

myDouble

result

1 Answer
1

It is working if you force the cast of the dynamic to double instead of letting the .ToDouble method find the appropriate type itself. Instead, do an explicit cast:

.ToDouble

for(var i = 0; i < result.Count; i++)
cumulativeAvg.Add(result.Take(i + 1).Average(r => (double)r.myDouble));


null

Cast()

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