how to add multiple values for a single parameters of stored procedure in c#..?

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C#

SELECT P.ProductId , P.ProductName , P.Description ,P.Image , C.CategoryName ,P.IsActive
FROM Product AS P
JOIN
Category AS C
ON
P.CategoryId=C.CategoryId
WHERE (@ProductName IS NULL OR ProductName like '%' + @ProductName + '%')
AND (@CategoryName IS NULL OR CategoryName= @CategoryName)
AND (@IsActive IS NULL OR IsActive=@IsActive)

this is my stored procedure i want null value and textbox values both to be passed in c# for product name ..how to do it..?