ExecuteReader: Connection 属性尚未初始化

Imports System.Data.SqlClient

Public Class Form1

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
SqlConnection1.Open()
Dim rdCustomers As SqlDataReader
rdCustomers = _
SqlCommand1.ExecuteReader(CommandBehavior.CloseConnection)
Do While rdCustomers.Read
Console.WriteLine("身份证号码:" & rdCustomers.GetString(0) & _
" 姓名：" & rdCustomers.GetString(1) & " 房号：" & rdCustomers.GetString(2))
Loop
rdCustomers.Close()
End Sub
End Class
错误代码行：rdCustomers = SqlCommand1.ExecuteReader(CommandBehavior.CloseConnection)

请问ExecuteReader()是什么意思？ ExecuteReader C# Sql 问题 ExecuteReader: Connection 属性尚未初始化 C# userReader = com.ExecuteReader();出错 关于using(sqldatareader sdr = cmd.executereader()) dr=comm.ExecuteReader(CommandBehavior.CloseConnection); -----C#里如何理解. C# 里"userReader = com.ExecuteReader();"出错