求解：asp.net与数据库连接问题！！！

Question

在Web.config中：
<connectionStrings>
<add name="EnterpriseWebConnectionString" connectionString="Data Source=.;Initial Catalog=Enterprise1;Integrated Security=SSPI"  providerName="System.Data.SqlClient"/>
</connectionStrings>单击按钮上传：
protected void btn_up_Click(object sender, EventArgs e)
{
            //检查上传文件不为空
            if (this.uploadfile.PostedFile.ContentLength > 0)
            {
                if (Page.IsValid)
                {
                    Boolean fileOK = false;
                    //设定上传文件的保存路径
                    string path = Server.MapPath("~/UpLoadFile/");
                    if (this.uploadfile.HasFile)
                    {
                        string fileExtension = System.IO.Path.GetExtension(this.uploadfile.FileName).ToLower();
                        string[] allowedExtensions = {".gif",".png",".jpeg",".jpg"};
                        for (int i = 0; i < allowedExtensions.Length; i++)
                        {
                            if (fileExtension == allowedExtensions[i])
                            {
                                fileOK = true;
                            }
                        }
                    }
                    if (fileOK)
                    {
                        this.uploadfile.PostedFile.SaveAs(path + this.uploadfile.FileName);
                        string filepath = "UpLoadFile/" + this.uploadfile.FileName;
                        string filesize = (this.uploadfile.PostedFile.ContentLength /1024).ToString() + " K Byte(s)";                        //string strConString=ConfigurationManager.AppSettings["EnterpriseWebConnectionString"];
                        //SqlConnection conn = new SqlConnection(strConString);                      SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["EnterpriseWebConnectionString"].ConnectionString);  
                       // SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationSettings.AppSettings["EnterpriseWebConnectionString"]);                        string insertFile = "INSERT INTO FileDownload(FileName,FileSize,Class,Introduce,dtTime, Filepath,DownCount)VALUES('" + this.txtfilename.Text.Trim() + "', '" + filesize + "', '" + this.ddClass.SelectedValue.ToString() + "', '" + this.txtfilecon.Text + "',GetDate(),'" + filepath + "',0)";
                        conn.Open();
                        // 创建数据库命令
                        SqlCommand cmdUpFile = new SqlCommand(insertFile, conn);                        SqlDataReader drUpFile = cmdUpFile.ExecuteReader(CommandBehavior.CloseConnection);                        drUpFile.Close();                        cmdUpFile.Connection = conn;                        cmdUpFile.ExecuteNonQuery();
                        conn.Close();                        Response.Write("<script>alert('添加成功!@')</script>");
                    }
                }
                else
                {
                    Response.Write("<script>alert(上传文件类型错误！')</script>");
                }
            }
        }

Answer 1

if (conn == null)
                {
                    conn = new SqlConnection(str);
                    conn.Open();
                }
                else if (conn.State == System.Data.ConnectionState.Closed)
                {
                    conn.Open();
                }
                else if (conn.State == System.Data.ConnectionState.Broken)
                {
                    conn.Close();
                    conn.Open();
                }

Answer 2

什么错误
使用数据库操作类
<add key="ConnectionString" value="Data Source=(local);Initial Catalog=Test;User ID=sa;Password=sa"/>

Answer 3

首先有：connectionStrings尚未初始化
然后又是：ExecuteNonQuery 要求已打开且可用的连接。连接的当前状态为已关闭。