你调用的对象是空的.请解决这个

问题描述

限时删除！！

public class ImageHandler : IHttpHandler {
    string strcon = ConfigurationManager.AppSettings["ConnectionString"].ToString();

    public void ProcessRequest (HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        context.Response.Write("Hello World");
        string imageid = context.Request.QueryString["ImID"];
        SqlConnection connection = new SqlConnection("Data Source=CIODEV03\\SQLEXPRESS;Initial Catalog=EmployeeDB;Integrated Security=True");
        connection.Open();
        SqlCommand command = new SqlCommand("select Image from Image1 where ImageId=" + imageid, connection);
        SqlDataReader dr = command.ExecuteReader();
        dr.Read();
        context.Response.BinaryWrite((Byte[])dr[0]);
        connection.Close();
        context.Response.End();
    }

    public bool IsReusable {
        get {
            return false;
        }
    }
}

错误..........

对象引用未设置为对象的实例.
说明:执行当前Web请求期间发生未处理的异常.请查看堆栈跟踪，以获取有关错误及其在代码中起源的更多信息.

异常详细信息:System.NullReferenceException:对象引用未设置为对象的实例.

源错误:

error..........

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 7:
Line 8:  public class ImageHandler : IHttpHandler {
Line 9:      string strcon = ConfigurationManager.AppSettings["ConnectionString"].ToString();
Line 10:
Line 11:     public void ProcessRequest (HttpContext context)

推荐答案

ConfigurationManager.AppSettings["ConnectionString"].ToString();

为空，因为您可能尚未在webconfig文件中对其进行初始化.

因此，尝试检查那里是否可以找到解决方案.

如果可以帮助您，则将其标记为您的答案，我可以查询.

谢谢

is blank as you may not have initialized it in the webconfig file.

So try to check there you may get the solution there.

If it helps you out then mark this as your answer and i am open to queries.

Thanks

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