Type Guesser

Guess the C# Types for untyped strings e.g. "12.123".

• Nuget Package
• License MIT

Usage

var guesser = new Guesser();
guesser.AdjustToCompensateForValue("-12.211");
var guess = guesser.Guess;

The resulting guess in this case would be:

Property	Value
guess.CSharpType	typeof(decimal)
guess.Size.NumbersBeforeDecimalPlace	2
guess.Size.NumbersAfterDecimalPlace	3
guess.Width	7

Guesser also handles adjusting it's guess based on multiple input strings e.g.

var guesser = new Guesser();
guesser.AdjustToCompensateForValue("1,000");
guesser.AdjustToCompensateForValue("0.001");
var guess = guesser.Guess;

Property	Value
guess.CSharpType	typeof(decimal)
guess.Size.NumbersBeforeDecimalPlace	4
guess.Size.NumbersAfterDecimalPlace	3
guess.Width	8

Once you have guessed a Type for all your strings you can convert all your values to the hard type:

var someStrings = new []{"13:11:59", "9AM"};
var guesser = new Guesser();
guesser.AdjustToCompensateForValues(someStrings);

var parsed = someStrings.Select(guesser.Parse).ToArray();

Assert.AreEqual(new TimeSpan(13, 11, 59), parsed[0]);
Assert.AreEqual(new TimeSpan(9, 0, 0), parsed[1]);

String parsing/converting is largely handled by the excellent Universal Type Converter project by t-bruning.

Guess Order

The order in which Types are tried is (DatabaseTypeRequest.PreferenceOrder):

• Bool
• Int
• Decimal
• TimeSpan
• DateTime
• String

If a string has been accepted as one category e.g. "12" (Int) and an incompatible string arrived e.g. "0.1" then the Guess is changes to either the new Type (Decimal) or to String (i.e. untyped) based on whether the old and new Types are in the same TypeCompatibilityGroup

For example Bool and DateTime are incompatible

"Y" => Bool
"2001-01-01" => DateTime

Guess: String

Guesses are never revised back up again (once you accept a Decimal you never get Int again but you might end up at String)

Zero Prefixes

If an input string is a number that starts with zero e.g. "01" then the estimate will be changed to System.String. This is intended behaviour since some codes e.g. CHI / Barcodes have valid zero prefixes. If this is to be accurately preserved in the database then it must be stored as string (See TestGuesser_PreeceedingZeroes). This also applies to values such as "-01"

Whitespace

Leading and trailing whitespace is ignored for the purposes of determining Type. E.g. " 0.1" is a valid System.Decimal. However it is recorded for the maximum Length required if we later fallback to System.String (See Test TestGuesser_Whitespace).

Strong Typed Objects

Guesser.AdjustToCompensateForValue takes a System.Object. If you are passing objects that are not System.String e.g. from a DataColumn that has an actual Type on it (e.g. System.Float) then Guesser will set the Guess.CSharpType to the provided object Type. It will still calculate the Guess.Size properties if appropriate (See test TestGuesser_HardTypeFloats).

The first time you pass a typed object (excluding DBNull.Value) then it will assume the entire input stream is strongly typed (See IsPrimedWithBonafideType). Any attempts to pass in different object Types in future (or if strings were previously passed in before) will result in a MixedTypingException.