Issue with C#.net code to print arabic on bixolon spp r300

Question

I facing an issue with C#.net code to print Arabic characters on bixolon printer spp r300.

I tried the following code but not it doesn't work, just printing question marks “?” instead of arabic characters. For English characters, it works fine.

BxlPrint.SetInterChrSet(BxlPrint.BXL_CS_WPC1256);

    BxlPrint.SetCharacterSet(BxlPrint.BXL_CS_WPC1256);
    BxlPrint.PrintText("واحد القبول صحة", BxlPrint.BXL_ALIGNMENT_CENTER, BxlPrint.BXL_FT_DEFAULT,
    BxlPrint.BXL_TS_0WIDTH | BxlPrint.BXL_TS_0HEIGHT);