图片转为二进制数组存入SQL数据库，但提示有进程未关闭,该怎么处理

/// <summary>
/// 存储事件：将图片转换为Byte数组并依据题号存储进相应字段中
/// </summary>
        private void button2_Click(object sender, EventArgs e)
        {
            this.imageByte = SetImageToByteArray(this.imageFileName);
        }
/// <summary>
///图片转换为二进制数组
/// </summary>
public byte[] SetImageToByteArray(string fileName)
        {
            FileStream fs = new FileStream(fileName, FileMode.Open);
            int streamLength = (int)fs.Length;
            byte[] image = new byte[streamLength];
            fs.Read(image, 0, streamLength);
            fs.Close();
            return image;
        }