Display Image in GridView with path in database with image enlarge option

<asp:ImageField DataImageUrlField="photo" > <ItemStyle Width="50px" Height ="50px" 
                    HorizontalAlign="Center" VerticalAlign="Middle" ></ItemStyle>
            </asp:ImageField>

i need to display image from database in gridview.  i have the above html and a select query executed from code behind which displays the image

i am storing the image path in the database table and image in a folder

Queries related to above

1. image size not able to set

2. the gridview image column will display image if the column data is not blank. but if its blank i have 2 default images  male image and female image

so if the field is blank i need to display one of the default images depending on the gender selected

3. if the image is clicked it should show enlarged image as popup