public SQLSyntax GetSQLSyntax()

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'"
    };
}

public async Task UsingSqlSyntaxToFormPlatformAgnosticQueries()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.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.
            }
        }
    });
}