Cllr Hendry, who represented the Pinkneys Green ward since 1991, died on August 26.
His Royal Borough colleagues attended the service at Waltham St Lawrence Parish Church.
Cllr Rayner said: "I got to know Wilson in 2005 when I was first elected. He was one of the first friendly faces that I met when I was a new councillor. He made me welcome and helped me get through my first meetings as a rookie.
"I spent many hours in meetings with him discussing Windsor planning applications. These were enjoyable and great times as we had similar views on planning and the greenbelt.
"The Council chamber will seem an empty place without him."
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The Met Office has issued a yellow alert for Windsor and Maidenhead, Slough and Wokingham, warning that rain moving eastwards across the south of the country may turn to snow in some places.