将数据从Access DB填充到vb.net数据集 [英] Populate data from Access DB to vb.net dataset

问题描述

大家好，

我有问题.

状况:
我已经声明了一个字符串来保存查询中的数据

Hi all,

I have a problem.

Situation:
I have declared a string to hold the data from a query

strSQL=GetPayment(strDateFrm,strDateTo)
cnCMD = New OleDbCommand(strSQL, cnDB)
cnCMD.CommandType = CommandType.Text
rdr = cnCMD.ExecuteReader
If Not (IsNothing(strSQL)) Then
                        If rdr.Read Then  -------> "problem occurs here"
                            While rdr.Read

我想问一个能解决我问题的人:
如果数据库中的数据为空，该怎么办?因为当数据库中不存在数据时，它将填充为DataSet的空白，并且DataReader将找不到任何内容，并跳过我在数据库中没有输入条件的步骤，它将填充"-NA-"字符串值. br/>
或者谁能​​告诉我将数据库中的数据插入到DataSet的其他代码.
我对在搜索引擎中找到的答案感到困惑，因为大多数情况下，它们会将数据放入ListView，DataGridView之类的文件中.
这让我感到困惑.

我使用对象objPayment作为介质从数据库检索数据并填写DataSet列.
例如:

I want to ask anyone who can solve me for:
If data from database is empty, what should I do? Because when data is not exist in database, it will fill empty to DataSet and DataReader will find nothing and skip the step where I put a condition if nothing in database, it will fill "-NA-" string value.

Or can anyone tell me the other code for inserting data from database to DataSet.
I''m confused about the answer that I found in search engine because mostly they put the data into something such as ListView, DataGridView.
It confuses me.

I use an object objPayment as medium to retrieve data from database and fill in DataSet column.
For example:

If Not (IsDBNull(rdr("intMPAJRecpNo"))) Then
         objChqDataRow.strReceiptNo = rdr("intMPAJRecpNo")
Else
         objChqDataRow.strReceiptNo = "- NA -"
End If

如果有人无法使用DataReader处理数据，请帮忙.

If someone has the other way from my way to manipulate data from using DataReader, kindly help me.

推荐答案

您应该首先测试rdr是否包含行.

通常我写:

You should first test that your rdr has rows.

Typically I write:

While rdr.HasRows ANDALSO rdr.Read
'... code ...
End While

如果您这样做:

If you do this:

If rdr.Read Then 
    While rdr.Read

您实际上是在两次调用.Read时跳过了一行(在IF上再次输入WHILE).

You are actually skipping a row as you are calling .Read twice (Once on IF and again entering your WHILE).

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