这里是我的真实代码。调试时出现错误，连接必须有效并打开。
[C0行的错误
testNamebox.Text = cmd.ExecuteScalar()很难从您的问题中确切指出您所犯的错误，但这是一个猜测。
在您的代码中，您有：
Private Sub ButtonX1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
Try
Dim totalResultEng As Int16 = 0
Dim totalResultFr As Int16 = 0
Dim time As Int16 = 0
frmSavingData.Show()
For i As Integer = 0 To Me.DataGridView1.RowCount - 1
If Me.DataGridView1.Rows(i).Cells(2).Value = "Polynucléaires neutrophiles" Or Me.DataGridView1.Rows(i).Cells(2).Value = "Polynucléaires éosinophiles" Or _
Me.DataGridView1.Rows(i).Cells(2).Value = "Polynucléaires basophiles" Or Me.DataGridView1.Rows(i).Cells(2).Value = "Lymphocytes" Or _
Me.DataGridView1.Rows(i).Cells(2).Value = "Monocytes" Then
totalResultEng = totalResultEng + Val(Me.DataGridView1.Rows(i).Cells(4).Value)
totalResultFr = totalResultFr + Val(Me.DataGridView1.Rows(i).Cells(3).Value)
time = time + 1
End If
Next
If totalResultEng <> 100 And time = 5 Then
MsgBox("Please Check English Resultn Of Test Hg !", MsgBoxStyle.OkOnly, "Total Result")
Exit Sub
End If
If totalResultFr <> 100 And time = 5 Then
MsgBox("Please Check French Result Of Test Hg !", MsgBoxStyle.OkOnly, "Total Result")
Exit Sub
End If
Dim cmd As MySqlCommand, bold As Integer = 0, checkprint As Int16 = 0
Dim testNamebox As New RichTextBox
testNamebox.Width = 500
testNamebox.Height = 50
For i As Integer = 0 To Me.DataGridView1.RowCount - 1
Dim fr_result As String
Dim eng_result As String
cmd = New MySqlCommand("select testName from Testdetail where testid =" & Me.DataGridView1.Rows(i).Cells(2).Tag, Setting.cn)
' cmd = New MySqlCommand("select testName from Testdetail where testid ='" & Me.DataGridView1.Rows(i).Cells(2).Tag & "'", Setting.cn)
testNamebox.Text = cmd.ExecuteScalar()
If testNamebox.Lines.GetUpperBound(0) > 0 Then 'control number of lines in RichTextBox
testNamebox.Text = Me.DataGridView1(3, i).Value.ToString
If testNamebox.Lines.GetUpperBound(0) > 0 Then
If IsNothing(Me.DataGridView1(4, i).Value) Then eng_result = "" Else eng_result = Me.DataGridView1(4, i).Value.ToString
If IsNothing(Me.DataGridView1(3, i).Value) Then fr_result = "" Else fr_result = Me.DataGridView1(3, i).Value.ToString
Else
If IsNothing(Me.DataGridView1(4, i).Value) Then eng_result = "" Else eng_result = "" + vbCrLf + Me.DataGridView1(4, i).Value.ToString
If IsNothing(Me.DataGridView1(3, i).Value) Then fr_result = "" Else fr_result = "" + vbCrLf + Me.DataGridView1(3, i).Value.ToString
End If
Else
If IsNothing(Me.DataGridView1(4, i).Value) Then eng_result = "" Else eng_result = Me.DataGridView1(4, i).Value.ToString
If IsNothing(Me.DataGridView1(3, i).Value) Then fr_result = "" Else fr_result = Me.DataGridView1(3, i).Value.ToString
End If
If Me.DataGridView1(7, i).Value = True Then bold = 1
If Me.DataGridView1(8, i).Value = True Then checkprint = 1
cmd = New MySqlCommand("Update invoicedetail set EngResult='" & _
eng_result.ToString.Replace("\", "\\").Replace("'", "''") & "', FrResult='" & fr_result.ToString.Replace("\", "\\").Replace("'", "''") & _
"',Bold='" & bold & "',checkprint='" & checkprint & "' where testid='" & Me.DataGridView1.Rows(i).Cells(2).Tag & "' and invoiceid='" & Me.DataGridView1.Rows(i).Cells(0).Tag & "'", Setting.cn)
cmd.ExecuteNonQuery()
If Me.DataGridView1.Rows(i).Cells(0).Value <> "" And Me.DataGridView1.Rows(i).Cells(8).Value = False Then
cmd = New MySqlCommand("Update invoicedetail set checkprint=0 where TestID = '" & Me.DataGridView1.Rows(i).Cells(2).Tag & "' and invoiceid='" & Me.DataGridView1.Rows(i).Cells(0).Tag & "'", Setting.cn)
cmd.ExecuteNonQuery()
ElseIf Me.DataGridView1.Rows(i).Cells(0).Value <> "" And Me.DataGridView1.Rows(i).Cells(8).Value = True Then
cmd = New MySqlCommand("Update invoicedetail set checkprint=1 where TestID = '" & Me.DataGridView1.Rows(i).Cells(2).Tag & "' and invoiceid='" & Me.DataGridView1.Rows(i).Cells(0).Tag & "'", Setting.cn)
cmd.ExecuteNonQuery()
End If
cmd.Dispose()
bold = 0
checkprint = 0
frmSavingData.Refresh()
Next
cmd = New MySqlCommand("Update invoicedetail set EngObservation=" & IIf(txtEnglishObservation.Text <> "", "'" & txtEnglishObservation.Rtf.Replace("'", "''").Replace("\", "\\") & "'", "NULL") & _
", FrObservation=" & IIf(txtFrenchObservation.Text <> "", "'" & txtFrenchObservation.Rtf.Replace("'", "''").Replace("\", "\\") & "'", "NULL") & _
" where testid='" & TestIDforupdate & "' and invoiceid='" & InvoiceNo & "'", Setting.cn) 'TestID
cmd.ExecuteNonQuery()
cmd.Dispose()
'' MsgBox("Save successed!")
'Me.Close()
frmSavingData.Dispose()
Catch ex As Exception
frmSavingData.Dispose()
MsgBox(ex.Message)
End Try
End Sub
我假设Setting.cn是您的连接字符串。如果是这样，看来您永远不会打开或关闭连接。
尝试一下：
cmd = New MySqlCommand("select testName from Testdetail where testid =" & Me.DataGridView1.Rows(i).Cells(2).Tag, Setting.cn)
testNamebox.Text = cmd.ExecuteScalar()
您能尝试这个吗？
select testName from Testdetail where testid ='" & Me.DataGridView1.Rows(i).Cells(2).Tag & "'", Setting.cn)
您的值在处理sql时应包含在单引号中