Writing bangla in rich textbox in C#

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C#

I am doing a project with C# in Bangla. Now when i write a line in Bangla in rich textbox ending with symbol '|'(দাঁড়ি) then the output comes as "[][][]". For example, if i write "আমি ভাত খাই।" then the output comes as "[][][] [][][] [][][]|". But if the end of the sentence does not end with '|' then the output is ok. That is, if i write "আমি ভাত খাই" then the output comes as "আমি ভাত খাই". Then what is the problem of using '|' at the end of the Bangla sentence in rich textbox. Even the use of '|' in textbox does not make any problem.So how can i write a Bangla sentence in rich textbox ending with'|'.