Problem using "Shape.STLength()" field in the CalculateStatistics method

StuartBricker

I am writing a reporting application so the boss can quickly get the number of linear miles in a variety of polyline feature classes. I am using the .CalculateStatistics method based on the examples on Github. The following code works precisely as intended for all numeric fields except "Shape.STLength()", which unfortunately is the field I need. The code is as follows:

<SPAN class="keyword token">double</SPAN> <SPAN class="token function">GetLength</SPAN><SPAN class="punctuation token">(</SPAN>FeatureClass fc<SPAN class="punctuation token">)</SPAN>
<SPAN class="punctuation token">{</SPAN>
    <SPAN class="keyword token">try</SPAN>
    <SPAN class="punctuation token">{</SPAN>
         <SPAN class="keyword token">using</SPAN> <SPAN class="punctuation token">(</SPAN>FeatureClassDefinition fcd <SPAN class="operator token">=</SPAN> fc<SPAN class="punctuation token">.</SPAN><SPAN class="token function">GetDefinition</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
         <SPAN class="punctuation token">{</SPAN>
             Field LengthField <SPAN class="operator token">=</SPAN> fcd<SPAN class="punctuation token">.</SPAN><SPAN class="token function">GetFields</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">FirstOrDefault</SPAN><SPAN class="punctuation token">(</SPAN>x <SPAN class="operator token">=</SPAN><SPAN class="operator token">></SPAN> x<SPAN class="punctuation token">.</SPAN>Name<SPAN class="punctuation token">.</SPAN><SPAN class="token function">Equals</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"Shape.STLength()"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN> <SPAN class="comment token">//"PIPEDIAM" and other numeric fields work fine, Shape.STLength() fails, as does fcd.GetLengthField();</SPAN>
             <SPAN class="keyword token">if</SPAN> <SPAN class="punctuation token">(</SPAN>LengthField <SPAN class="operator token">==</SPAN> <SPAN class="keyword token">null</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">return</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
             Debug<SPAN class="punctuation token">.</SPAN><SPAN class="token function">WriteLine</SPAN><SPAN class="punctuation token">(</SPAN>LengthField<SPAN class="punctuation token">.</SPAN>Name<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN> <SPAN class="comment token">// Output is "Shape.STLength()" as expected</SPAN>

             StatisticsDescription SumDesc <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">StatisticsDescription</SPAN><SPAN class="punctuation token">(</SPAN>LengthField<SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">List</SPAN><SPAN class="operator token"><</SPAN>StatisticsFunction<SPAN class="operator token">></SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN> StatisticsFunction<SPAN class="punctuation token">.</SPAN>Sum <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
             TableStatisticsDescription tsd <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">TableStatisticsDescription</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">List</SPAN><SPAN class="operator token"><</SPAN>StatisticsDescription<SPAN class="operator token">></SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN> SumDesc <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

             <SPAN class="keyword token">return</SPAN> fc<SPAN class="punctuation token">.</SPAN><SPAN class="token function">CalculateStatistics</SPAN><SPAN class="punctuation token">(</SPAN>tsd<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">FirstOrDefault</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN>StatisticsResults<SPAN class="punctuation token">.</SPAN><SPAN class="token function">FirstOrDefault</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN>Sum<SPAN class="punctuation token">;</SPAN> <SPAN class="comment token">// exception is thrown on this line</SPAN>
          <SPAN class="punctuation token">}</SPAN>
     <SPAN class="punctuation token">}</SPAN>
     <SPAN class="keyword token">catch</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="token class-name">Exception</SPAN> ex<SPAN class="punctuation token">)</SPAN>
     <SPAN class="punctuation token">{</SPAN>
             ArcGIS<SPAN class="punctuation token">.</SPAN>Desktop<SPAN class="punctuation token">.</SPAN>Framework<SPAN class="punctuation token">.</SPAN>Dialogs<SPAN class="punctuation token">.</SPAN>MessageBox<SPAN class="punctuation token">.</SPAN><SPAN class="token function">Show</SPAN><SPAN class="punctuation token">(</SPAN>ex<SPAN class="punctuation token">.</SPAN><SPAN class="token function">ToString</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"Error"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
             <SPAN class="keyword token">return</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
     <SPAN class="punctuation token">}</SPAN>
<SPAN class="punctuation token">}</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

The exception that is thrown on line 14 is as follows:

Again, it is noteworthy that everything works fine when I set the fieldname on line 7 to any numeric (double) field other than Shape.STLength(). 

Wolf

Your assumption was correct.  The dev team for the statistics class(es) is planning a fix for one of the upcoming releases.  It's too late for the fix to make it into the 2.5 release though.