The Problem
Our C# application sends a query to Solr server, and parses the response and generate graph report. Today the application throws error: Input string was not in a correct format. in one test environment.

At first thought, we thought it is due to the language and region settings, as shown in the post: C# Parsing is Regional(Culture) Sensitive

But we found out that in customer environment, it doesn’t always fail, just failed in some rare cases. 
The Analysis
We re-executed the Solr stats query, and found some unexpected numbers in the response: the min value of the stats query is negative. This should not happen in normal cases. 

The real problem here is why these negative value comes from, and we should reject invalid value when push data to Solr.  We will fix the previous problem. 

But why it fails when C# parses the response? As the same code is used when parse all double value from solr response. It may contain negative value.

Checked the code and run it with the negative number.

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string value = "-10.01";
double dvalue = double.Parse(value, System.Globalization.NumberStyles.AllowExponent | System.Globalization.NumberStyles.AllowDecimalPoint);

It failed. Now it’s clear that this is because Double.Parse(String, NumberStyles).
From Double.Parse Method (String, NumberStyles)
Converts the string representation of a number in a specified style to its double-precision floating-point number equivalent.

As we only specify AllowExponent and AllowDecimalPoint. It will disallow sign symbol. It will only take non negative value. Give it negative value, it will fail with exception. This code should be updated to use Double.parse(String s).

The Double.Parse Method allows string in format: [ws][sign][integral-digits[,]]integral-digits[.[fractional-digits]][E[sign]exponential-digits][ws]

C# Parsing is Regional(Culture) Sensitive
Solr: Extend StatsComponent to Support stats.query, stats.facet and facet.topn

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