Description:
In the German and other languages there are several ways to display some special character. No matter which option is used in the data or the search box, they should find each other. This can be easily implemented by using the CurrentCulture for the string comparison: StringComparison.CurrentCultureIgnoreCase

Userstory:
The letter ü can be represented as a letter (U+00FC) or as a decomposition of u (U+0075) and a combining diaeresis (U+0308). There is a data set which uses the decomposed ü (U+0075, U+0308). The GridSearchBox searches for a ü (U+00FC). The data set with the decomposed ü is to be found.

The data set is currently not found because you are using the following for the string comparison: 
StringComparison.OrdinalIgnoreCase
User input should always use the current culture!
Please fix the error by using : StringComparison.CurrentCultureIgnoreCase