Need Help for Updating database in vb.net - sql

Question

Someone knows why I got an exception when the code running at cmd.ExecuteNonQuery()? when I update Date, it runs perfectly but when I update the Finish date, I got that error.
This is the code
Call connection()
If txt_UpCom.Text = "" Or cbCom.SelectedItem = "" Then
If txt_ComNew.Enabled = True Then
MessageBox.Show("Please fill the entire data!")
End If
Else
Try
Dim str As String
If cbCom.SelectedItem = "Date" Or cbCom.SelectedItem = "Finish Date" Then
Dim comdate As String = dateCom.Value.ToString("yyyy-MM-dd")
str = "UPDATE complain SET " & cbCom.SelectedItem & "= '" & comdate & "' WHERE ComplainID = '" & txt_UpCom.Text & "'"
Else
str = "UPDATE complain SET " & cbCom.SelectedItem & " = '" & txt_ComNew.Text & "' WHERE ComplainID = '" & txt_UpCom.Text & "'"
End If
cmd = New MySql.Data.MySqlClient.MySqlCommand(str, conn)
cmd.ExecuteNonQuery()
msgBoxSuccess.ShowDialog()
conn.Close()
Catch ex As Exception
MessageBox.Show("Unable to Update")
End Try
End If
This is the table in database

Answer 1

As #Jacek Wróbel mentioned in the comments, you should keep the column names between [] (square brackets) or "" (double quots). The same thing goes for table names (or any other SQL objects for that matter).
Long story short, change this part of your code:
If cbCom.SelectedItem = "Date" Or cbCom.SelectedItem = "Finish Date" Then
Dim comdate As String = dateCom.Value.ToString("yyyy-MM-dd")
str = "UPDATE complain SET " & cbCom.SelectedItem & "= '" & comdate & "' WHERE ComplainID = '" & txt_UpCom.Text & "'"
Else
str = "UPDATE complain SET " & cbCom.SelectedItem & " = '" & txt_ComNew.Text & "' WHERE ComplainID = '" & txt_UpCom.Text & "'"
End If
to this:
If cbCom.SelectedItem = "Date" Or cbCom.SelectedItem = "Finish Date" Then
Dim comdate As String = dateCom.Value.ToString("yyyy-MM-dd")
str = "UPDATE `complain` SET `" & cbCom.SelectedItem & "` = '" & comdate & "' WHERE `ComplainID` = '" & txt_UpCom.Text & "'"
Else
str = "UPDATE `complain` SET `" & cbCom.SelectedItem & "` = '" & txt_ComNew.Text & "' WHERE `ComplainID` = '" & txt_UpCom.Text & "'"
End If
Note: I prefer to keep things consistant, so I added [] to each object whether it contains spaces or not.