Question

所以我试着根据我的sob服务器中链接的组合框来填充我的文本框。

每次我在ComboBox中选择一个项目时都会出现此错误。

connectionstring属性尚未初始化

    Private Sub CBuname_SelectedIndexChanged(sender As Object, e As EventArgs) Handles CBuname.SelectedIndexChanged
    Dim cmd As New SqlCommand()
    Dim Reader As SqlDataReader
    Try
        con.Open()
        Dim sql As String = "Select * From CoAdminData where Username='" & CBuname.Text & "'"
        cmd = New SqlCommand(sql, con)
        Reader = cmd.ExecuteReader

        If Reader.HasRows() Then
            While Reader.Read
                txtSID.Text = Reader("StudentID")
                txtFirstname.Text = Reader("Firstname")
                txtLastname.Text = Reader("Lastname")
            End While
        End If
        con.Close()
    Catch ex As Exception
        MsgBox(ex.Message)
    Finally
        con.Dispose()
    End Try

End Sub

Answer 1

只是提供一个可以使用/修改的完整示例和模板。我已经评论了你需要做的一切不要在公共类中声明con，而是尝试使用每种方法打开和关闭它。你可以在其他地方公开宣布constr，这可以为你节省一些写作。 HTH

var CryptoJS = require("crypto-js");

// the input values
var base64Header = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9";
var base64Payload = "eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ";
var secret = "hONPMX3tHWIp9jwLDtoCUwFAtH0RwSK6";

// two hashes from different online tools
var signatureJWTIO = "3pIaKksiX9Zv8Jg-hWbrD24VhL36hBIFaNpA4fVx29M";
var onlineCaluclatedHS256 =  "de921a2a4b225fd66ff0983e8566eb0f6e1584bdfa84120568da40e1f571dbd3";

// hash calculation with Crypto-JS. 
// The two replace expressions convert Base64 to Base64url format by replacing '+' with '-' 
// and stripping the '=' padding
var base64Signature = CryptoJS.HmacSHA256(base64Header + "." + base64Payload , secret).toString(CryptoJS.enc.Base64).replace(/\+/g,'-').replace(/\=+$/m,'');

// converting the online calculated value to Base64 representation
var base64hash = new Buffer(onlineCaluclatedHS256, 'hex').toString('base64').replace(/\+/g,'-').replace(/\=+$/m,'');


// the results:
console.log("Signature from JWT.IO             : " + signatureJWTIO);
console.log("NodeJS calculated hash            : " + base64Signature);
console.log("online calulated hash (converted) : " + base64hash);

connectionstring porperty尚未初始化

1 个答案: