I'm trying to create sql database that contains

Image Id (int)
Imagename (varchar(50))
Image (image)

and in aspx write in upload button this code:

protected void btnUpload_Click(object sender, EventArgs e)
{
    //Condition to check if the file uploaded or not
    if (fileuploadImage.HasFile)
    {
        //getting length of uploaded file
        int length = fileuploadImage.PostedFile.ContentLength;

        //create a byte array to store the binary image data
        byte[] imgbyte = new byte[length];

        //store the currently selected file in memeory
        HttpPostedFile img = fileuploadImage.PostedFile;

        //set the binary data
        img.InputStream.Read(imgbyte, 0, length);

        string imagename = txtImageName.Text;

        //use the web.config to store the connection string
        SqlConnection connection = new SqlConnection(strcon);
        connection.Open();

        SqlCommand cmd = new SqlCommand("INSERT INTO Image (ImageName,Image) VALUES (@imagename,@imagedata)", connection);
       cmd.Parameters.Add("@imagename", SqlDbType.VarChar, 50).Value = imagename;
       cmd.Parameters.Add("@imagedata", SqlDbType.Image).Value = imgbyte;

       int count = cmd.ExecuteNonQuery();
       connection.Close();

       if (count == 1)
       {
           BindGridData();
           txtImageName.Text = string.Empty;
           ScriptManager.RegisterStartupScript(this, this.GetType(), "alertmessage", "javascript:alert('" + imagename + " image inserted successfully')", true);
       }
    }
}

When I'm uploading a new image I need to first check if this image already exists in database and if it doesn't exist save that in database.

Please how I can do that?