public SQLSyntax GetSQLSyntax()

{
  await QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    using (Table table = geodatabase.OpenDataset<Table>("TableWithChineseCharacters"))
    {
      // This will fail with many database systems that expect Latin characters by default
      string incorrectWhereClause = "颜色 = '绿'";

      // Correct solution is to prepend the 'National String Prefix' to the attribute value
      // For example, with SQL Server this value is 'N'
      // This value is obtained using the SQLSyntax class
      string nationalStringPrefix = "";
      SQLSyntax sqlSyntax = geodatabase.GetSQLSyntax();
      nationalStringPrefix = sqlSyntax.GetSupportedStrings(SQLStringType.NationalStringPrefix).First();

      // This Where clause will work
      QueryFilter queryFilter = new QueryFilter()
      {
        WhereClause = "颜色 = " + nationalStringPrefix + "'绿'"
      };
    }
  });
}

{
  await QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri("C:\\Data\\LocalGovernment.gdb"))))
    using (FeatureClass featureClass = geodatabase.OpenDataset<FeatureClass>("FacilitySite"))
    {
      SQLSyntax sqlSyntax = geodatabase.GetSQLSyntax();
      string substringFunctionName = sqlSyntax.GetFunctionName(SQLFunction.Substring);
      string upperFunctionName = sqlSyntax.GetFunctionName(SQLFunction.Upper);
      string substringfunction = string.Format("{0}({1}(FCODE, 1, 6)) = 'SCHOOL'", upperFunctionName,
        substringFunctionName);

      QueryFilter queryFilter = new QueryFilter
      {
        WhereClause = substringfunction
      };
      using (Selection selection =
             featureClass.Select(queryFilter, SelectionType.ObjectID, SelectionOption.Normal))
      {
        // work with the selection.
      }
    }
  });
}