c# - 如何检查字节数组是否为空？

Question

我正在为 GetSourceAttachment 方法下载 word 文件。当此方法返回空字节时，我的字节 Attachment 数组会出错:

Object reference not set instance of object

当我在 if 条件下检查 Attachment 的长度时出现错误。

谁能帮我默认初始化字节数组，然后检查长度？

try
{
        byte[] Attachment = null ;

        string Extension = string.Empty;
        ClsPortalManager objPortalManager = new ClsPortalManager();
        Attachment = objPortalManager.GetSourceAttachment(Convert.ToInt32(hdnSourceId.Value), out Extension);
        if (Attachment.Length > 0 && Attachment != null)
        {
            DownloadAttachment("Attacment", Attachment, Extension);
        }
        else
        {
            ClientScript.RegisterStartupScript(typeof(Page), "SymbolError", "<script type='text/javascript'>alert('Attachment is not Uploaded !');</script>");
        }            
}
catch
{

}

Answer 1

就这样

if (Attachment != null  && Attachment.Length > 0)

来自 && Operator

The conditional-AND operator (&&) performs a logical-AND of its bool operands, but only evaluates its second operand if necessary.