如何使用vb.net从Access db提取数据并将其放入文本框？

Question

Hi guys I'm trying to search an employee information using SQL from MS Access, and hoping to put the fname lname and such details in their respective textbox which correspond to a specific employee's ID number. I have managed to make the SQL work but I don't know how to extract files from my sql statement and place it inside .text(text box), can you please guide me? Thanks

Here is my code so far: (UPDATED my code) got an error message : Additional information: ExecuteReader: Connection property has not been initialized. Highlighting Reader below. How can i fix this? I'm trying to extract data and place it into the textbox? Thanks

Private Sub eNumText_SelectedIndexChanged(sender As Object, e As EventArgs) Handles eNumText.SelectedIndexChanged


        Dim dbSource = "Data Source= C:\Databse\Company_db.accdb"
        con.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0; Data Source= c:\Databse\Company_db.accdb"

        Dim sqlQuery As String
        Dim sqlCommand As New OleDbCommand
        Dim sqlAdapter As New OleDbDataAdapter
        Dim Table As New DataTable

        Dim empNum As String
        Dim empFname As String
        Dim empLname As String
        Dim empDept As String
        Dim empStat As String
        Dim empYears As String

        empNum = eNumText.Text
        empFname = empFnameText.Text
        empLname = empLnameText.Text
        empDept = DeptText.Text
        empStat = StatText.Text
        empYears = yearstext.Text

        sqlQuery = "SELECT * FROM tbl_empinfo WHERE EmpID like empNum"

        With sqlCommand
            .CommandText = sqlQuery
            .Connection = con
            .Parameters.AddWithValue("EmpID", empNum)
            With sqlAdapter
                .SelectCommand = sqlCommand
                .Fill(Table)
            End With
            With DataGridView1
                .DataSource = Table
            End With
        End With

        Dim path = "Data Source= C:\Databse\Company_db.accdb"
        Dim command = "SELECT * FROM tbl_empinfo WHERE EmpID like empNum"
        QueryData(path, command)


        con.Close()

    End Sub
    Private Sub QueryData(PathDb As String, command As String)
        Using connection As New System.Data.OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & PathDb)
            Using da As New System.Data.OleDb.OleDbCommand(command, connection)
                connection.Open()

                Dim reader = da.ExecuteReader()
                If reader.Read() Then
                    empFnameText.Text = reader("fname")
                    empLnameText.Text = reader("lname")
                End If

                connection.Close()
            End Using
        End Using
    End Sub

Answer 1

for this, you need only this classes: Connection, Command, Reader. Other classes in the code in question, some are redundant and some are required but in complicated than a simple case presentation.

Private Sub QueryData(PathDb As String, command As String)
    Using connection As New System.Data.OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & PathDb)
        Using com As New System.Data.OleDb.OleDbCommand(command, connection)
            connection.Open()

            Dim reader = com.ExecuteReader()
            If reader.Read() Then
                TextBox1.text = reader("fname")
                TextBox2.text = reader("lname")
            End If

            connection.Close()
        End Using
    End Using
End Sub

call the method so:

Dim path = "C:\Databse\Company_db.accdb"
Dim command = "SELECT * FROM tbl_empinfo WHERE EmpID like empNum"
QueryData(path, command)

---

EDIT - Use parameters:

Private Sub QueryData(PathDb As String, command As String, id As String)
    Using connection As New System.Data.OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & PathDb)
        Using com As New System.Data.OleDb.OleDbCommand(command, connection)
            com.Parameters.AddWithValue("", id)

            connection.Open()

            Using reader = com.ExecuteReader()
                If reader.Read() Then
                    TextBox1.Text = reader("fname")
                    TextBox2.Text = reader("lname")
                End If
            End Using

            connection.Close()
        End Using
    End Using
End Sub

Call the method:

Dim path = "C:\Databse\Company_db.accdb"
Dim command = "SELECT * FROM tbl_empinfo WHERE EmpID = ?"
Dim empNum = "..."
QueryData(path, command, empNum)