c# error - Can not convert Array to byte array

I am trying cast a Json data to byte array and then save it in SQL image field, code is below

public string Post([FromBody] dynamic data)
{
        foreach (var item in data)
        {
               imgPhoto1 = (byte[])item["Photo1"];
        }
 }

But getting error Can not convert Array to byte array

 byte[] imgPhoto1 = (byte[])item["Photo1"];

Values in field item["Photo1"] is look like below

 [255,216,255,224]

any help will be appreciated

var obj = item["Photo1"].ToObject<byte[]>();