Passing multiple values from custom dropdown exposed filter to the view query (IN clause)

I made a custom module with exposed filter which represent list of file extension from table “field_data_field_file_download_link”.For example I have a “pdf” list item and I want this item to hold all fid from above mention table.So when I pressed on dropdown list and select a pdf option view need to show me all article which have asociated pdf files.
Problem is when I have something like this:
<option value="'342','234','234'">pdf</option>
When I select this option View query added slash on every value.So I have query like this WHERE fid IN(‘342 ‘,’234’).This slash produce problem and sql statements canot return all the article with this ‘fid’ number.
How can I resolve this?

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