即時通訊設計我的網頁,因爲我已經輸入了書籍ID並鍵入 Nameofthebook。然後單擊按鈕本書的堆棧都可以是去到另一個頁面,然後不可用是顯示錯誤消息是本書不可用我的項目(圖書管理系統)Asp.net如何糾正錯誤
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
public partial class Bookcheck : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button1_Click(object sender, EventArgs e)
{
string constr = null;
constr =
ConfigurationManager.ConnectionStrings["librarymanagementconnetionstring"].ConnectionStrin
g
;
SqlConnection cnn = new SqlConnection(constr);
cnn.Open();
DataSet ds = new DataSet();
DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter("SELECT*FROM BOOKREGISTRATIONDETAILS WHERE
bookId='" + txtid.Text.Trim() + "'AND Nameofbook='" + txtnb.Text.Trim() + "'",
constr);
da.Fill(ds);
if (ds.Tables[0].Rows.Count > 0)
{
Response.Redirect("Issueofbook.aspx");
}
else
{
Msg.Text = "NO book available";
Msg.Visible = true;
}
}
}
}
My error
NULL reference exception in un handle by the user
constr =
ConfigurationManager.ConnectionStrings["librarymanagementconnetionstring"].ConnectionStrin
g;
請儘量將代碼格式化爲可讀狀態。提示:在Visual Studio中,選擇要包含的代碼,按 + ,直到最外層的範圍沒有縮進,複製並粘貼到編輯器中,選擇代碼,然後按 + 。這看起來很整齊。 –
2011-03-17 10:13:28
格式化消息時,請確保您編寫了完整的代碼,然後選擇了整個代碼,然後單擊工具欄按鈕將其標記爲代碼段。現在你的帖子是不可讀的,至少對我而言。 – Tengiz 2011-03-17 10:14:46