打呼噜磨牙怎么办:cmd.ExecuteScalar()转化为string

标准表达式中数据类型不匹配。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.Data.OleDb.OleDbException: 标准表达式中数据类型不匹配。

源错误:

行 21: conn.Open();
行 22: OleDbCommand cmd = new OleDbCommand("select shopName from showshop where shopID='" + shopid + "'", conn);
行 23: string s = cmd.ExecuteScalar().ToString();
行 24: cmd.CommandText = "select * from shoping where id='" + shopid + "'";
行 25: OleDbDataReader odr = cmd.ExecuteReader();

源文件: d:\shoptest\showshop.aspx.cs 行: 23

堆栈跟踪:

[OleDbException (0x80040e07): 标准表达式中数据类型不匹配。]
System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult(tagDBPARAMS dbParams, Object& executeResult) +177
System.Data.OleDb.OleDbCommand.ExecuteCommandText(Object& executeResult) +194
System.Data.OleDb.OleDbCommand.ExecuteCommand(CommandBehavior behavior, Object& executeResult) +56
System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) +105
System.Data.OleDb.OleDbCommand.ExecuteScalar() +97
showshop.Page_Load(Object sender, EventArgs e) in d:\shoptest\showshop.aspx.cs:23
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +13
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +45
System.Web.UI.Control.OnLoad(EventArgs e) +80
System.Web.UI.Control.LoadRecursive() +49
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3743

同时我还用过this.lblname.text=convert.tostring(cmd.executescalar());
但是都不行，急求啊！~~