怎样使用参数查询

如果想通过一张表的某一个字段查询出这张表的全部信息,并用datagrid显示出来,应该怎么做?有哪位高人能提供一段源代码例子给偶啊(偶的抽象思维很弱,一般要看到实例才理解得比较快,呵呵) --------------------编程问答-------------------- “通过一张表的某一个字段查询出这张表的全部信息”是什么意思？ --------------------编程问答-------------------- 写个存储过程不就行了
imports system.data.sqlclient

dim cnn as new sqlconnection
dim dataset as new dataset

cnn.connectionstring="server=srvname;database=dbname;uid=sa;pwd="
cnn.open

dim adapter as sqldataadapter=new (spname,cnn)
dim pr as new sqlparameter

pr.name='@item'
pr.dbtype=system.type.gettype("System.string")
pr.type=input
adapter.parameters.add(pr)

adapter.fill(dataset)
datagrid1.datasource=dataset.table(0) --------------------编程问答-------------------- 楼主问题更抽象哦
看不懂啊。
是用一个字段还是用多个字段？ --------------------编程问答-------------------- 说不清，何以道明？ --------------------编程问答-------------------- 应该就是加条件吧，条件是有一个字段限定的。
那存储过程怎么加到代码里呢？ --------------------编程问答-------------------- ado.net + sql 应该就是这样的：

Imports System.Data
Imports System.Data.OleDb
Public Class Form1
    Dim conn As New OleDbConnection
    Dim connstr, sql As String
    Dim cmd As OleDbCommand
    Dim da As New OleDbDataAdapter
    Dim tbl As New DataTable

    Private Sub Conn_DB()
        connstr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Application.StartupPath & "\123.mdb"
        conn.ConnectionString = connstr
        Try
            conn.Open()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub

    Private Sub DoQuery()
        Dim Insql As String
        If conn.State = ConnectionState.Closed Then Conn_DB()
        sql = "select * from mydata where "
        Insql = "f1 like '%" & TextBox1.Text & "%'"
        sql &= Insql
        Insql = "and f2 like '%" & TextBox2.Text & "%'"
        sql &= Insql
        Insql = "and f3 like '%" & TextBox3.Text & "%'"
        sql &= Insql
        cmd = New OleDbCommand(sql, conn)
        da.SelectCommand = cmd
        tbl.Clear()
        da.Fill(tbl)
        DataGridView1.DataSource = tbl
    End Sub

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        conn.Close()
        conn.Dispose()
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        DoQuery()
    End Sub

    Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Convert.ToInt32(e.KeyChar) = 13 Then
            TextBox2.Focus()
            TextBox2.SelectAll()
        End If

    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        DoQuery()
    End Sub

    Private Sub TextBox2_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox2.KeyPress
        If Convert.ToInt32(e.KeyChar) = 13 Then
            TextBox3.Focus()
            TextBox3.SelectAll()
        End If
    End Sub

    Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.TextChanged
        DoQuery()
    End Sub

    Private Sub TextBox3_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox3.KeyPress
        If Convert.ToInt32(e.KeyChar) = 13 Then
            TextBox1.Focus()
            TextBox1.SelectAll()
        End If
    End Sub

    Private Sub TextBox3_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox3.TextChanged
        DoQuery()
    End Sub
End Class

简单的做了个多字段的查询，显示控件使用datagridview ,你看看吧 --------------------编程问答-------------------- 在前台程序中,使用参数化查询,如:
strMsg = "EXEC sp_executesql " _
        & "N'SELECT UserCode,UserName,[Password]库FROM RB_Users WHERE UserCode=@P1'," _
        & "N'@P1 NVARCHAR(30)',@P1='" & sLoginName & "'"
Con.Execute strMsg,lAffected

!Con为已打开的连接,lAffected为接收受此查询影响的行数.

补充：.NET技术 ,  VB.NET