如何使用 C# 中的 OLEDB 驱动程序查询带有 .NDX 索引文件的 Foxpro .DBF 文件 [英] How to query a Foxpro .DBF file with .NDX index file using the OLEDB driver in C#

问题描述

我有一个 Foxpro .DBF 文件.我正在使用 OLEDB 驱动程序读取 .DBF 文件.我可以查询 DBF 并利用其 .CDX 索引文件(因为它会自动打开).我的问题是我想用 .NDX 索引文件(打开 .DBF 时不会自动打开)来查询它.如何使用 OLEDB 驱动程序在 C# 中打开 .NDX 文件，导致 DBF 非常大，无法搜索没有索引的记录?谢谢大家！这是我用来读取 DBF 的代码.

I have a Foxpro .DBF file. I am using OLEDB driver to read the .DBF file. I can query the DBF and utilize its .CDX index file(cause it is automatically opened). My problem is that I want to query it with the .NDX index file (which is not automatically opened when the .DBF is opened). How can I open the .NDX file in C# using OLEDB driver cause the DBF is really big to search for a record without the index? Thanks all! Here is the code I am using to read the DBF.

OleDbConnection oleDbConnection = null;
        try
        {
            DataTable resultTable = new DataTable();
            using (oleDbConnection = new OleDbConnection("Provider=VFPOLEDB.1;Data Source=P:\\Test\\DSPC-1.DBF;Exclusive=No"))
            {
                oleDbConnection.Open();
                if (oleDbConnection.State == ConnectionState.Open)
                {
                    OleDbDataAdapter dataApdapter = new OleDbDataAdapter();
                    OleDbCommand command = oleDbConnection.CreateCommand();

                    string selectCmd = @"select * from P:\Test\DSPC-1  where dp_file = '860003'";
                    command.CommandType = CommandType.Text;
                    command.CommandText = selectCmd;

                    dataApdapter.SelectCommand = command;
                    dataApdapter.Fill(resultTable);
                    foreach(DataRow row in resultTable.Rows)
                    {
                        //Write the data of each record 
                    }
                }
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            try
            {
                oleDbConnection.Close();
            }
            catch (Exception e)
            {
                Console.WriteLine("Failed to close Oledb connection: " + e.Message);
            }
        }

推荐答案

ndx 文件在默认情况下不会被打开，这些已经成为过去，为什么不简单地将索引添加到 CDX 中.如果它不是一个选项，那么 DRapp 的 ExecScript 建议就是您可以做的.他非常接近.您可以这样做:

ndx files wouldn't be opened by default and those are a thing of the past really, why wouldn't you simply add your index to your CDX. If it is not an option, then ExecScript suggestion by DRapp is what you can do. He was very close. Here is how you could do that:

string myCommand = @"Use ('P:\Test\DSPC-1') alias myData
Set Index To ('P:\Test\DSPC-1_Custom.NDX')
select * from myData ;
  where dp_file = '860003' ;
  into cursor crsResult ;
  nofilter
SetResultset('crsResult')";

DataTable resultTable = new DataTable();
using (oleDbConnection = new OleDbConnection(@"Provider=VFPOLEDB;Data Source=P:\Test"))
{
  oleDbConnection.Open();
  OleDbCommand command = new OleDbCommand("ExecScript", oleDbConnection);
  command.CommandType = CommandType.StoredProcedure;
  command.Parameters.AddWithValue("code", myCommand);

  resultTable.Load(cmd.ExecuteReader());
  oleDbConnection.Close();
}

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