How to Split Comma Separated Values in SQL Server

Create FUNCTION [dbo].[Split_Function]
(@String varchar(MAX),@ImageNameByUser varchar(MAX)=null, @Delimiter char(1),@QuestionId bigint,@ID1 int)
returns @temptable TABLE (RightOptions varchar(MAX),NotInUse varchar(MAX),QuestionId bigint,QuestionOptionId bigint,RightAnswerId bigint)
as
begin
    declare @idx int
    declare @slice varchar(8000)

    ,@slice2 varchar(8000)
    ,@idx2 int

    select @idx = 1
    select @idx2 = 1
    if len(@String)<1 or @String is null return
        while @idx!= 0
        begin
            set @idx = charindex(@Delimiter,@String)
            set @idx2 = charindex(@Delimiter,@ImageNameByUser)
            if @idx!=0
                set @slice = left(@String,@idx - 1)
            else
                set @slice = @String
            if @idx2!=0
                set @slice2 = left(@ImageNameByUser,@idx2 - 1)
            else
                set @slice2 = @ImageNameByUser
            --If(IsNull(@ImageNameByUser,'@@')!='@@')
            --if(len(@slice)>0 And len(@slice2)>0 )
            --Else
            if(len(@slice)>0)
                BEGIN
                    SET @ID1=@ID1+1
                    declare @RightAnsId bigint
                    Select @RightAnsId=isnull(QuestionOptionId,0) from tblQuestionOption where OptionDetail = LTRIM(RTRIM(@slice)) And QuestionId=@QuestionId
                    insert into @temptable(RightOptions,NotInUse,QuestionId,QuestionOptionId,RightAnswerId)
                    values(LTRIM(RTRIM(@slice)),LTRIM(RTRIM(@slice2)),@QuestionId,@RightAnsId,@ID1)
                END
                set @String = right(@String,len(@String) - @idx)
            if len(@String) = 0 break
                set @ImageNameByUser = right(@ImageNameByUser,len(@ImageNameByUser) - @idx2)
            if len(@ImageNameByUser) = 0 break
        end
    return
end