当我从数据库表中检索图像时，出现以下错误.图像以二进制格式存储在表中 [英] while i am retrieving the image from the db table i am getting the below error.image is stored in the table in binary format

问题描述

byte[] bytes = (byte[])drc[0]["img"];

这里drc是数据行集合

错误信息:

无法将类型为"System.DBNull"的对象转换为类型为"System.Byte []".

here drc is the data row collection

erro info:

Unable to cast object of type ''System.DBNull'' to type ''System.Byte[]''.

推荐答案

这很明显:错误消息非常明确.
您的SQL查询返回第0行的"img"空白字段.

您的数据库不包含图像，或者您的查询错误.

It''s pretty obvious: the error message is very explicit.
Your SQL query is returning an empty field for "img" on row 0.

Either your database does not contain an image, or your query is wrong.

要在标记中进行操作:

to do it in markup:

<telerik:radbinaryimage runat="server" id="rbi" datavalue="<%# ((System.Data.Linq.Binary) Eval("imageFull")).ToArray() %>" xmlns:telerik="#unknown" /> 

或动态执行:

or do it dynamically:

var product = (from p in products
               select p).First();//.First() = LIMIT 1 in sql, which in turn makes the product variable singular and usable like this:
rsi.DataValue = product.imageFull.ToArray();

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