Parameter is not valid error

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C#

picturebox

//code for saving image into sql server 2008 r2//////
byte[] img = null;
FileStream fs = new FileStream(imgLoc,FileMode.Open,FileAccess.Read);
BinaryReader br=new BinaryReader(fs);
img = br.ReadBytes((int)fs.Length);


string conn = "data source=.;Initial catalog=RMSDB;user=sa;password=ibs;";
SqlConnection con = new SqlConnection(conn);
con.Open();
string cmdd = String.Format("INSERT INTO Employees (Emp_Pic_ImageData) VALUES('{0}')", @img);

SqlCommand cmd = new SqlCommand(cmdd, con);

cmd.Parameters.Add(new SqlParameter("@img",img));
int tempss = cmd.ExecuteNonQuery();


//code for retrival of image from sql server////////////


string sql = String.Format("Select Emp_Pic_ImageData From Employees where Emp_Id='{0}'", TxtBoxId.Text);
SqlCommand cmd = new SqlCommand(sql, con);
SqlDataReader reader = cmd.ExecuteReader();
reader.Read();
if (reader.HasRows)
{
byte[] img = (byte[])(reader[0]);
if (img == null)
{
PicboxEmployee.Image = null;
}
else
{
MemoryStream mstrm = new MemoryStream(img);
PicboxEmployee.Image = new System.Drawing.Bitmap(mstrm); //there is error of parameter is not valid.

}
}
else
{

MessageBox.Show("this not exists");

}