索引超出范围的异常未得到处理 [英] index out of range exception was unhandled

问题描述

存储程序

--------------------

STORED PROCEDURE
--------------------

ALTER PROCEDURE USP_Get_Invoice_No

AS

BEGIN
         SELECT MAX(invoice_no) from tbl_cleaning_purchase_categories


END

< br $>


CLASS LIBRARY（使用N层架构）

------------------ --------------------------

CLASS LIBRARY(USING N-TIER ARCHITECTURE)
--------------------------------------------

// GET INVOICE NO
  private const string USP_Get_Invoice_No = "USP_Get_Invoice_No"
  
  public IDataReader GET_INVOICE_NO()
        {
            DbCommand com = db.GetStoredProcCommand(USP_Get_Invoice_No);
            return db.ExecuteReader(com);
        }

代码文件

-------------------

CODE FILE
-------------------

public void LoadInvoiceNo()
       {

int InvoiceNO;
            IDataReader drInvoiceNo;
            drInvoiceNo = obj.GET_INVOICE_NO();
                while(drInvoiceNo.Read())
                {
                    string val = drInvoiceNo["invoice_no"].ToString(); ------------error
                    if (val == "")
                    {
                        InvoiceNO = Convert.ToInt32(txt_InvoiceNo.Text);
                        InvoiceNO = 1;
                    }
                    else
                    {
                        InvoiceNO = Convert.ToInt32(drInvoiceNo["invoice_no"].ToString());
                        txt_InvoiceNo.Text = (InvoiceNO + 1).ToString();

                    }
}

推荐答案

1）你绝对确定 invoice_no 是要返回的列/键的正确名称？如果在密钥集合中找不到该项目，则 .ToString（）调用将触发您收到的错误。

2）看到你可以尝试这种方式：

1) Are you absolutely sure that invoice_no is the correct name for the column/key being returned? If that item cannot be found in the keys collection, then the .ToString() call will trigger the error you are receiving.
2) Seeing that you are allowing for a non return option, you could try this way:

drInvoiceNo = obj.GET_INVOICE_NO();
while(drInvoideNo.Read())
{
   if( string.IsNullOrEmpty(drInvoiceNo["invoice_no"] )
   {
      InvoiceNO = Convert.ToInt32(txt_InvoiceNo.Text);
      // Why are you overriding what you set in the previous line here?
      InvoiceNO = 1;  
   }
   else
   {
      // A better way to handle the conversion.
      if( !Int32.TryParse( drInvoiceNo["invoice_no"].ToString(), out InvoiceNO ) )
      {
         InvoiceNO = ??;// Set some default value here because conversion has failed.
      }
      txt_InvoiceNo.Text = (InvoiceNO + 1).ToString();
   }
}

以Marcus的解决方案为基础：

难道不是存储过程别名 MAX（invoice_no）的结果如：

Building on Marcus'' solution:
Shouldn''t the Stored Procedure alias the result of the MAX(invoice_no) like:

ALTER PROCEDURE USP_Get_Invoice_No
AS
BEGIN
         SELECT MAX(invoice_no) as "Max_invoice_no" from tbl_cleaning_purchase_categories
END

然后使用Max_invoice_no作为列/ key：

and then use "Max_invoice_no" as the column/key:

drInvoiceNo = obj.GET_INVOICE_NO();
while (drInvoiceNo.Read())
{
   var max_invoice_no = drInvoiceNo["Max_invoice_no"].ToString(); 
   if ( string.IsNullOrEmpty(max_invoice_no) )
   {
      max_invoice_no = txt_InvoiceNo.Text;
   }
   // A better way to handle the conversion.
   if ( !Int32.TryParse( max_invoice_no, out InvoiceNO ) )
   {
      InvoiceNO = ??;// Set some default value here because conversion has failed.
   }
   txt_InvoiceNo.Text = (InvoiceNO + 1).ToString();
}

另一种可能性，如果你不能改变存储过程，就是获得中的第0个索引drInvoiceNo 因为Max是存储过程返回的唯一值。

Another possibility, if you cannot change the stored procedure, would be to just get the 0-th index in drInvoiceNo since the Max is the only value returned from the stored procedure.

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