vb.net 中 mysql 数据库的 For Each 循环

Question

I'm trying to create a reminder that notifies users the number of days before a chemical expires. I'm trying to retrieve the data in my database using ForEach loop, but I can't get the syntax right.

For Each chemicalName as DataRow In chemicalinventory.Rows

For some reason, the error: name ' chemicalinventory ' not declared keeps popping up.

From what I seen online, that is supposed to be the table name. Am I coding it wrong? Please answer if you know what's the error.

Answer 1

You cannot just directly start querying tables in this manner. You need to select your data from the database table and use it to fill a DataTable . You can then loop through the rows of this DataTable to get what you're after.

There are many ways to do that, but here is a very basic setup - granted, you'd need to specify a connection string in your Web.Config, and modify the SQL query to be relative to your needs.

Dim sqlConnection1 As New SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings("YOUR_CONNECTION_STRING").ConnectionString)
Dim cmd As New SqlCommand
cmd.CommandType = Data.CommandType.Text
cmd.CommandText = "SELECT * FROM chemicals"
cmd.Connection = sqlConnection1

Dim DataAdapter As New SqlDataAdapter
DataAdapter.SelectCommand = cmd

Dim chemicalInventory As New DataTable()
DataAdapter.Fill(chemicalInventory)

For each row as DataRow in chemicalInventory.rows
   Response.write(row.item("column_name"))
Next