.net - iam 创建带有 sql 连接 bt 错误的登录页面会发生 {dr} 值类型无法转换

Question

导入 System.Data.SqlClient 部分类登录继承 System.Web.UI.Page

Dim con As SqlConnection
Dim cmd As SqlCommand
Shared dr As SqlDataReader
'Shared da As SqlDataAdapter

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    con = New SqlConnection("Data source=USER-PC\SQLEXPRESS; Initial catalog= icare; Integrated security=True")
    cmd = New SqlCommand("select * from userlogin where UserName='" + TextBox1.Text + "' and Password='" + TextBox3.Text + "'", con)
    SqlDataReader(dr)
    con.Open()
    dr = cmd.ExecuteReader()

    If (dr.Read()) Then
        TextBox1.Text = dr("user Name").ToString
        TextBox2.Text = dr("Password").ToString
        'If (TextBox1.Text = TextBox1.Text And TextBox3.Text = TextBox2.Text) Then
        '    Response.Redirect("Defaulft.aspx")
    Else
        Response.Redirect("Home.master")
        lbl.Visible = True
        lbl.Text = "Invalid USERNAME & PASSWORD"
    End If
    'End If
End Sub

结束类导入 System.Data.SqlClient 部分类登录继承 System.Web.UI.Page

Dim con As SqlConnection
Dim cmd As SqlCommand
Shared dr As SqlDataReader
'Shared da As SqlDataAdapter

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    con = New SqlConnection("Data source=USER-PC\SQLEXPRESS; Initial catalog= icare; Integrated security=True")
    cmd = New SqlCommand("select * from userlogin where UserName='" + TextBox1.Text + "' and Password='" + TextBox3.Text + "'", con)
    SqlDataReader(dr)
    con.Open()
    dr = cmd.ExecuteReader()

    If (dr.Read()) Then
        TextBox1.Text = dr("user Name").ToString
        TextBox2.Text = dr("Password").ToString
        'If (TextBox1.Text = TextBox1.Text And TextBox3.Text = TextBox2.Text) Then
        '    Response.Redirect("Defaulft.aspx")
    Else
        Response.Redirect("Home.master")
        lbl.Visible = True
        lbl.Text = "Invalid USERNAME & PASSWORD"
    End If
    'End If
End Sub

结束类导入 System.Data.SqlClient 部分类登录继承 System.Web.UI.Page

Dim con As SqlConnection
Dim cmd As SqlCommand
Shared dr As SqlDataReader
'Shared da As SqlDataAdapter

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    con = New SqlConnection("Data source=USER-PC\SQLEXPRESS; Initial catalog= icare; Integrated security=True")
    cmd = New SqlCommand("select * from userlogin where UserName='" + TextBox1.Text + "' and Password='" + TextBox3.Text + "'", con)
    SqlDataReader(dr)
    con.Open()
    dr = cmd.ExecuteReader()

    If (dr.Read()) Then
        TextBox1.Text = dr("user Name").ToString
        TextBox2.Text = dr("Password").ToString
        'If (TextBox1.Text = TextBox1.Text And TextBox3.Text = TextBox2.Text) Then
        '    Response.Redirect("Defaulft.aspx")
    Else
        Response.Redirect("Home.master")
        lbl.Visible = True
        lbl.Text = "Invalid USERNAME & PASSWORD"
    End If
    'End If
End Sub

结束类导入 System.Data.SqlClient 部分类登录继承 System.Web.UI.Page

Dim con As SqlConnection
Dim cmd As SqlCommand
Shared dr As SqlDataReader
'Shared da As SqlDataAdapter

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    con = New SqlConnection("Data source=USER-PC\SQLEXPRESS; Initial catalog= icare; Integrated security=True")
    cmd = New SqlCommand("select * from userlogin where UserName='" + TextBox1.Text + "' and Password='" + TextBox3.Text + "'", con)
    SqlDataReader(dr)
    con.Open()
    dr = cmd.ExecuteReader()

    If (dr.Read()) Then
        TextBox1.Text = dr("user Name").ToString
        TextBox2.Text = dr("Password").ToString
        'If (TextBox1.Text = TextBox1.Text And TextBox3.Text = TextBox2.Text) Then
        '    Response.Redirect("Defaulft.aspx")
    Else
        Response.Redirect("Home.master")
        lbl.Visible = True
        lbl.Text = "Invalid USERNAME & PASSWORD"
    End If
    'End If
End Sub

结束类导入 System.Data.SqlClient 部分类登录继承 System.Web.UI.Page

Dim con As SqlConnection
Dim cmd As SqlCommand
Shared dr As SqlDataReader
'Shared da As SqlDataAdapter

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    con = New SqlConnection("Data source=USER-PC\SQLEXPRESS; Initial catalog= icare; Integrated security=True")
    cmd = New SqlCommand("select * from userlogin where UserName='" + TextBox1.Text + "' and Password='" + TextBox3.Text + "'", con)
    SqlDataReader(dr)
    con.Open()
    dr = cmd.ExecuteReader()

    If (dr.Read()) Then
        TextBox1.Text = dr("user Name").ToString
        TextBox2.Text = dr("Password").ToString
        'If (TextBox1.Text = TextBox1.Text And TextBox3.Text = TextBox2.Text) Then
        '    Response.Redirect("Defaulft.aspx")
    Else
        Response.Redirect("Home.master")
        lbl.Visible = True
        lbl.Text = "Invalid USERNAME & PASSWORD"
    End If
    'End If
End Sub

结束类导入 System.Data.SqlClient 部分类登录继承 System.Web.UI.Page

Dim con As SqlConnection
Dim cmd As SqlCommand
Shared dr As SqlDataReader
'Shared da As SqlDataAdapter

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    con = New SqlConnection("Data source=USER-PC\SQLEXPRESS; Initial catalog= icare; Integrated security=True")
    cmd = New SqlCommand("select * from userlogin where UserName='" + TextBox1.Text + "' and Password='" + TextBox3.Text + "'", con)
    SqlDataReader(dr)
    con.Open()
    dr = cmd.ExecuteReader()

    If (dr.Read()) Then
        TextBox1.Text = dr("user Name").ToString
        TextBox2.Text = dr("Password").ToString
        'If (TextBox1.Text = TextBox1.Text And TextBox3.Text = TextBox2.Text) Then
        '    Response.Redirect("Defaulft.aspx")
    Else
        Response.Redirect("Home.master")
        lbl.Visible = True
        lbl.Text = "Invalid USERNAME & PASSWORD"
    End If
    'End If
End Sub

结束类

Answer 1

您的代码似乎不完整（可能会被截断？） - 无论如何，我建议您执行逐步跟踪（F5）。如果可以连接到数据库，请确定有问题的语句。从您的姿势中不清楚哪条线失败了。

你的代码：

SqlDataReader（博士）

对我来说模棱两可。

检查：MSDN-Retrieving Data Using a DataReader以获得与您的案例类似的清晰示例。