Question

我正在使用VB.NET和SQL Server 2005，我想从数据库中编写一个文本文件，如。

打开文本文件，从数据库中读取数据，然后写入文本文件。

代码。

cmd = New SqlCommand("SELECT ID, Name, Dept from table", con)
dr = cmd.ExecuteReader

While dr.Read()

    Dim data As String
    data = File.ReadAllText(dr.Item("PersonID"))
    File.WriteAllText("D:\test.txt", data)
End While

上面的代码显示错误，如何编写文本文件

VB.NET代码帮助

Answer 1

在您的代码中，您实际上并没有从数据库中读取数据。试试这个：

Using writer = New StreamWriter("d:\test.txt")
    While dr.Read()
        Dim id = dr.GetInt32(0)
        Dim name = dr.GetString(1)
        Dim dept = dr.GetString(2)

        writer.WriteLine(String.Format("{0} {1} {2}", id, name, dept))
    End While
End Using

Answer 2

cmd = New SqlCommand("SELECT ID, Name, Dept from table", con)
dr = cmd.ExecuteReader

Dim sb as new StringBuilder

While dr.Read()

    ''Let's read line by line and Append it to our StringBuilder
    sb.AppendLine(
           String.Format("{0} | {1} | {2} | {3}", 
                   dr.item("ID"), dr.item("Name"), dr.item("Dept") ))

End While

''Now that we have all data in our StringBuilder, lets put into our file

File.WriteAllLines("D:\test.txt", sb.ToString())

<强> P.S 即可。来自一个C＃家伙...请验证代码是否正确:)（C＃代码如下）

using (SqlConnection con = new SqlConnection("my Connection String"))
{
    using (SqlCommand cmd = new SqlCommand())
    {
        cmd.Connection = con;
        cmd.CommandType = System.Data.CommandType.Text;
        cmd.CommandText = "SELECT ID, Name, Dept from table";

        con.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        StringBuilder sb = new StringBuilder();

        while (dr.Read())
            // Let's read line by line and Append it to our StringBuilder
            sb.AppendLine(
                String.Format("{0} | {1} | {2} | {3}",
                    dr["ID"], dr["Name"], dr["Dept"]));

        // Now that we have all data in our StringBuilder, lets put into our file
        File.WriteAllLines("D:\test.txt", sb.ToString());
    }
}

Answer 3

File.ReadAllText如果从文件中读取。

File.WriteAllText会将所有内容写入文件，覆盖其中的内容。

你需要得到这样的数据：

data = dr.Item("PersonID").ToString()

写作时，您可能想要append the text：

File.AppendAllText("D:\test.txt", data);

更有效的方法是遍历数据，在内存中构建整个数据集（在每行末尾添加换行符），然后使用File.WriteAllText一次性写入所有数据。我假设数据量不大，因为这种方法将使用更多内存，但会减少磁盘IO。

写一个文本文件

3 个答案: