请教！！！什么叫：ConnectionString 属性尚未初始化。 ？？？

[lxqparadise]

在检测数据库中是否有重复ID的时候出现的
源代码：

'检查数据库中是否有重复ID
Function checkid(ByVal sender As Object, ByVal value As String) As Boolean

Dim strconnection As String
Dim ds As DataSet = New DataSet
Dim mycommand As SqlDataAdapter = New SqlDataAdapter("selectuserid", strconnection)
mycommand.SelectCommand.Parameters.Add(New SqlParameter("@user_id", SqlDbType.VarChar, 15))
mycommand.SelectCommand.CommandType = CommandType.StoredProcedure
mycommand.SelectCommand.Parameters("@user_id").Value = value
mycommand.Fill(ds, "userinfo")
If ds.Tables("userinfo").Rows.Count > 0 Then
myboolean = False
Else
myboolean = True
End If

End Function

执行到mycommand.Fill(ds, "userinfo")语句时提示错误：
ConnectionString 属性尚未初始化。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.InvalidOperationException: ConnectionString 属性尚未初始化。

源错误:


行 184： mycommand.SelectCommand.CommandType = CommandType.StoredProcedure
行 185： mycommand.SelectCommand.Parameters("@user_id").Value = value
行 186： mycommand.Fill(ds, "userinfo")
行 187： If ds.Tables("userinfo").Rows.Count > 0 Then
行 188： myboolean = False


源文件: C:\Inetpub\wwwroot\yhzc\yonghuzhuce.aspx.vb 行: 186

堆栈跟踪:


[InvalidOperationException: ConnectionString 属性尚未初始化。]
System.Data.SqlClient.SqlConnection.Open() +433
System.Data.Common.DbDataAdapter.QuietOpen(IDbConnection connection, ConnectionState& originalState) +44
System.Data.Common.DbDataAdapter.FillFromCommand(Object data, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +304
System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +77
System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable) +36
yhzc.WebForm1.checkid(Object sender, String value) in C:\Inetpub\wwwroot\yhzc\yonghuzhuce.aspx.vb:186
yhzc.WebForm1.Button1_Click(Object sender, EventArgs e) in C:\Inetpub\wwwroot\yhzc\yonghuzhuce.aspx.vb:166
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +108
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +57
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain() +1277


请教各位！！！

[panyee]

'实例化一个连接
Dim conn As SqlConnection = new SqlConnection(strconnection)

Dim mycommand As SqlDataAdapter = New SqlDataAdapter("selectuserid", conn)

[lxqparadise]

还是不行！！在连接数据库之前我以及实例化了！

[loulanlouzhu]

ConnectionString 属性尚未初始化

-->没有初始化连接字符串!

[panyee]

strconnection = "server=......."
连接串赋值

[lxqparadise]

已经赋值了。
快乐王子你的信箱多少？我把代码传过去你看看到底怎么回事？

[loulanlouzhu]

你把代码贴出来!肯定是没赋值!

[chenqianliang]

Function checkid(ByVal sender As Object, ByVal value As String) As Boolean

' Dim strconnection As String
'改为
dim strconnection as SqlConnection
strconnection=new SqlConnection("连接字符串，比如：data source=localhost;uid=sa;pwd=;")
Dim ds As DataSet = New DataSet
Dim mycommand As SqlDataAdapter = New SqlDataAdapter("selectuserid", strconnection)
mycommand.SelectCommand.Parameters.Add(New SqlParameter("@user_id", SqlDbType.VarChar, 15))
mycommand.SelectCommand.CommandType = CommandType.StoredProcedure
mycommand.SelectCommand.Parameters("@user_id").Value = value
mycommand.Fill(ds, "userinfo")
If ds.Tables("userinfo").Rows.Count > 0 Then
myboolean = False
Else
myboolean = True
End If

End Function

[loulanlouzhu]

string ConnectionString;
ConnectionString= "连接字符串，比如：data source=localhost;uid=sa;pwd=;");
SqlConnection myConnection = new SqlConnection(ConnectionString);

[lxqparadise]

源代码：

Dim strconnection As String = "server=localhost;uid=sa;pwd=;database=softlab"
Dim myboolean As Boolean

'单击提交按钮触发的事件
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim value As String
If Page.IsValid Then
If txtuserid.Text = "" Or txtpassword.Text = "" Or txtpassword2.Text = "" Then
lblmessage.Text = "必须输入用ID和密码"
lblmessage.ForeColor = Color.Red
ElseIf txtpassword.Text <> txtpassword2.Text Then
lblmessage.Text = "两次输入的密码不一致！"
lblmessage.ForeColor = Color.Red
Else
value = txtuserid.Text.ToString
Response.Write(txtuserid.Text)
checkid(e, value)
If myboolean Then
adduser()
Else
lblmessage.Text = "错误：注册失败。已经有了此用户，请另选其它的ID名"
lblmessage.ForeColor = Color.Red
End If
End If
End If

End Sub

Function checkid(ByVal sender As Object, ByVal value As String) As Boolean

Dim strconnection As String
Dim ds As DataSet = New DataSet
Dim mycommand As SqlDataAdapter = New SqlDataAdapter("selectuserid", connectionstring)
mycommand.SelectCommand.Parameters.Add(New SqlParameter("@user_id", SqlDbType.VarChar, 40))
mycommand.SelectCommand.CommandType = CommandType.StoredProcedure
mycommand.SelectCommand.Parameters("@user_id").Value = value
mycommand.Fill(ds, "userinfo")
If ds.Tables("userinfo").Rows.Count > 0 Then
myboolean = False
Else
myboolean = True
End If

End Function

[lxqparadise]

我的赋值语句在代码的最上边。所有的执行过程都可以直接调用。
不用执行一个过程赋值一次。

[panyee]

'注释掉这句 Dim strconnection As String


connectionstring这个在哪实例化怎么没看着？

[lxqparadise]

知道哪儿错了。
多谢各位大虾～！！