无法将类型'object'隐式转换为'System.Data.OleDb.OleDb.DataReader' [英] cannot implicitly convert type 'object' to 'System.Data.OleDb.OleDb.DataReader'

问题描述

我修改了我的代码并摆脱了''DB''错误。但是，现在我有了新的错误;

无法将类型'对象'隐式转换为'System.Data.OleDb.OleDb.DataReader'存在显式转换（您是否缺少演员？）

代码：

 使用系统; 
 使用 System.Web; 
 使用 System.Web.Profile; 
 使用 System.Web.UI; 
 使用 System.Data.OleDb; 
 使用 System.Data.SqlClient; 
 使用 System.Web.UI.HtmlControls; 
 使用 System.Web.UI.WebControls; 
 
  public   partial   class  MasterPage2：MasterPage 
 {
  protected   void  Page_Load（ object  sender，EventArgs e）
 {
  this  .litdate.Text = DateTime.Now。 ToString（  D）; 
  if （ this  .Page.User.Identity.Name.ToString（）！= < span class =code-string> ）
 {
  string  strSQL =  string  .Format（ 选择来自AgentBasicInfo的Agent_current_bal，其中Agent_ID ='{0}'，此 .Page.User.Identity.Name.ToString（）。ToLower（））。的ToString（）; 
 
 OleDbConnection conn =  new  OleDbConnection（  ASPNETDB）; 
 OleDbCommand cmd =  new  OleDbCommand（strSQL，conn）; 
 conn.Open（）; 
 OleDbDataReader dr1 = cmd.ExecuteScalar（）; 
 此 .litbal.Text = dr1; 
} 
 其他 
 {
 此 .up12 .Visible =  false ; 
} 
 此 .submenu.Visible = 此 .Page.User.Identity .Name.ToString（）==   admin; 
  this  .lblCreatedBy.Text =  已创建作者：Christopher Mutoborokho; 
} 
 
} 

解决方案

cmd.ExecuteScalar（）; 无法转换为OleDbDataReader - 您尝试返回单个值而不是datareader，因此请使用类似

  float  dr1 =（ float ）cmd.ExecuteScalar（）; 

你还需要将行 this.litbal.Text = dr1; 更改为

 this.litbal.Text = dr1.ToString（）; 

或

使用

 OleDbDataReader dr1 = cmd.ExecuteReader（）; 

您需要更改此行：

 OleDbDataReader dr1 = cmd.ExecuteScalar（）; 

到此：

 OleDbDataReader dr1 = cmd.ExecuteReader （）

这将返回select语句中的行。然后你必须将这个阅读器加载到这样的数据表中：

 DataTable dt = new DataTable（）; 
 dt.Load（dr1）; 

然后，您可以遍历数据表行以获取所需的数据。

I have modified my code and got rid of the ''DB'' error. However, now i have a new errors;

"cannot implicitly convert type 'object' to 'System.Data.OleDb.OleDb.DataReader' An explicit conversion exists(are you missing a cast?)"

The code:

using System;
using System.Web;
using System.Web.Profile;
using System.Web.UI;
using System.Data.OleDb;
using System.Data.SqlClient;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;

public partial class MasterPage2 : MasterPage
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.litdate.Text = DateTime.Now.ToString("D");
        if (this.Page.User.Identity.Name.ToString() != "")
        {
            string strSQL = string.Format("Select Agent_current_bal from AgentBasicInfo where Agent_ID='{0}'", this.Page.User.Identity.Name.ToString().ToLower()).ToString();

            OleDbConnection conn = new OleDbConnection("ASPNETDB");
 OleDbCommand cmd = new OleDbCommand(strSQL, conn);
 conn.Open();
 OleDbDataReader dr1 = cmd.ExecuteScalar();
            this.litbal.Text = dr1;
        }
        else
        {
            this.up12.Visible = false;
        }
        this.submenu.Visible = this.Page.User.Identity.Name.ToString() == "admin";
        this.lblCreatedBy.Text = "Created By: Christopher Mutoborokho";
    }

}

解决方案

cmd.ExecuteScalar(); cannot be cast to an OleDbDataReader - you are trying to return a single value not a datareader so use something like

float dr1 = (float)cmd.ExecuteScalar();

you will also need to change the line this.litbal.Text = dr1; to

this.litbal.Text = dr1.ToString();

OR
use

OleDbDataReader dr1 = cmd.ExecuteReader();

You need to change this line:

OleDbDataReader dr1 = cmd.ExecuteScalar();

to this:

OleDbDataReader dr1 = cmd.ExecuteReader()

That will return the rows from your select statement. Then you will have to load that reader into a datatable like this:

DataTable dt = new DataTable();
 dt.Load(dr1);

You can then iterate through your datatable rows to get the data you want.

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