VB.NET无法更新datagridview中的SQL数据

Question

我尝试了很多方法，但问题依然无法解决。

我的目的是点击搜索按钮后，datagridview会在一定条件下显示来自SQL数据库的数据。

当我第一次点击搜索按钮，它的作品。但后来我点击搜索按钮第二次datagridview显示空白（我改变了一些条件，如不同的行号等）。

请帮帮我！谢谢你这么多

这里是我的VB代码：

Private Sub search_btn_Click(sender As Object, e As EventArgs) Handles search_btn.Click 


    Dim connectionString As String = "Data Source=xxx.xx.xx.xxx;Initial Catalog=QCDB;User ID=sa;Password=xxxxx;" 
    'different content of FROMTIME AND TOTIME 
    If FROMTIME = " " And TOTIME = " " Then 
     sql = "SELECT * FROM PRODUCT WHERE (SAMPLE_SOURCE = @SOURCE OR @SOURCE = 'all') AND (PRO_TYPE = @TYPE OR @TYPE = 'all') AND (PRO_NAME = @NAME OR @NAME = 'all')" & 
     "AND (EMBOSS_TOP = @EMBOSS_TOP OR @EMBOSS_TOP = 'all') AND (EMBOSS_BOTTOM = @EMBOSS_BOTTOM OR @EMBOSS_BOTTOM = 'all') AND (LINE_NO = @LINE_NO OR @LINE_NO = 'all')" & 
     "AND (SHIFT = @SHIFT OR @SHIFT = 'all') AND (STD_THICK = @STAND_THICKNESS OR @STAND_THICKNESS = 'all') AND (COLOR = @COLOR OR @COLOR = 'all') " 
    ElseIf FROMTIME = " " And TOTIME <> " " Then 
     FROMTIME = DateTime.Now.AddYears(-15).ToString("yyyy-MM-dd") 
     sql = "SELECT * FROM PRODUCT WHERE (SAMPLE_SOURCE = @SOURCE OR @SOURCE = 'all') AND (PRO_TYPE = @TYPE OR @TYPE = 'all') AND (PRO_NAME = @NAME OR @NAME = 'all')" & 
     "AND (EMBOSS_TOP = @EMBOSS_TOP OR @EMBOSS_TOP = 'all') AND (EMBOSS_BOTTOM = @EMBOSS_BOTTOM OR @EMBOSS_BOTTOM = 'all') AND (LINE_NO = @LINE_NO OR @LINE_NO = 'all')" & 
     "AND (SHIFT = @SHIFT OR @SHIFT = 'all') AND (STD_THICK = @STAND_THICKNESS OR @STAND_THICKNESS = 'all') AND (COLOR = @COLOR OR @COLOR = 'all') AND PRO_DATE BETWEEN'" & FROMTIME & "' AND '" & TOTIME & "'" 
    ElseIf FROMTIME <> " " And TOTIME = " " Then 
     TOTIME = DateTime.Now.ToString("yyyy-MM-dd") 
     sql = "SELECT * FROM PRODUCT WHERE (SAMPLE_SOURCE = @SOURCE OR @SOURCE = 'all') AND (PRO_TYPE = @TYPE OR @TYPE = 'all') AND (PRO_NAME = @NAME OR @NAME = 'all')" & 
     "AND (EMBOSS_TOP = @EMBOSS_TOP OR @EMBOSS_TOP = 'all') AND (EMBOSS_BOTTOM = @EMBOSS_BOTTOM OR @EMBOSS_BOTTOM = 'all') AND (LINE_NO = @LINE_NO OR @LINE_NO = 'all')" & 
     "AND (SHIFT = @SHIFT OR @SHIFT = 'all') AND (STD_THICK = @STAND_THICKNESS OR @STAND_THICKNESS = 'all') AND (COLOR = @COLOR OR @COLOR = 'all') AND PRO_DATE BETWEEN'" & FROMTIME & "' AND '" & TOTIME & "'" 
    Else 
     sql = "SELECT * FROM PRODUCT WHERE (SAMPLE_SOURCE = @SOURCE OR @SOURCE = 'all') AND (PRO_TYPE = @TYPE OR @TYPE = 'all') AND (PRO_NAME = @NAME OR @NAME = 'all')" & 
     "AND (EMBOSS_TOP = @EMBOSS_TOP OR @EMBOSS_TOP = 'all') AND (EMBOSS_BOTTOM = @EMBOSS_BOTTOM OR @EMBOSS_BOTTOM = 'all') AND (LINE_NO = @LINE_NO OR @LINE_NO = 'all')" & 
     "AND (SHIFT = @SHIFT OR @SHIFT = 'all') AND (STD_THICK = @STAND_THICKNESS OR @STAND_THICKNESS = 'all') AND (COLOR = @COLOR OR @COLOR = 'all') AND PRO_DATE BETWEEN'" & FROMTIME & "' AND '" & TOTIME & "'" 
    End If 

    Dim connection As New SqlConnection(connectionString) 
    Dim cmd = New SqlCommand(sql, connection) 
    Dim dataadapter As New SqlDataAdapter(cmd) 
    Dim ds As New System.Data.DataSet() 

    cmd.Parameters.AddWithValue("@SOURCE", sample_source_combox.Text) 
    cmd.Parameters.AddWithValue("@TYPE", product_type_combox.Text) 
    cmd.Parameters.AddWithValue("@NAME", product_name_combox.Text) 
    cmd.Parameters.AddWithValue("@EMBOSS_TOP", embossing_top_combox.Text) 
    cmd.Parameters.AddWithValue("@EMBOSS_BOTTOM", embossing_bottom_combox.Text) 
    cmd.Parameters.AddWithValue("@LINE_NO", line_number_combox.Text) 
    cmd.Parameters.AddWithValue("@SHIFT", shift_serach_combox.Text) 
    cmd.Parameters.AddWithValue("@STAND_THICKNESS", std_thickness_combox.Text) 
    cmd.Parameters.AddWithValue("@COLOR", color_search_combox.Text) 

    Try 
     connection.Open() 

     dataadapter.Fill(ds, "PRODUCT") 
     DataGridView1.Columns.Clear() 
     DataGridView1.Refresh() 

     With Me.DataGridView1 
      .RowsDefaultCellStyle.BackColor = Color.AliceBlue 
      .AlternatingRowsDefaultCellStyle.BackColor = Color.White 
     End With 

     connection.Close() 
     DataGridView1.DataSource = ds.Tables(0) 
     DataGridView1.AutoGenerateColumns = False 

    Catch ex As Exception 
     MessageBox.Show(ex.ToString) 
    End Try 
End Sub 

Answer 1

我花了一段时间来发现问题，并在这样做，我不得不重新写的方式我通常会匹配做事情（下面）。你可以直接跳过下面的解释，但我认为这是值得的，因为它确实解决了代码中涉及日期范围的两个巨大问题。

Private Sub search_btn_Click(sender As Object, e As EventArgs) Handles search_btn.Click 
    Dim sql As String = "SELECT * FROM PRODUCT WHERE 1=1" 
    Dim connectionString As String = "Data Source=xxx.xx.xx.xxx;Initial Catalog=QCDB;User ID=sa;Password=xxxxx;" 

    Try 

     Using connection As New SqlConnection(connectionString), _ 
       cmd As New SqlCommand(sql, connection) 

      'Match each of the parameter types and lengths to the columns 
      If sample_source_combox.Text <> "all" Then 
       cmd.CommandText += " AND SAMPLE_SOURCE = @SOURCE" 
       cmd.Paramters.Add("@SOURCE", SqlDbType.NVarChar, 15).Value = sample_source_combox.Text 
      End If 

      If product_type_combox.Text <> "all" Then 
       cmd.CommandText += " AND PRO_TYPE = @TYPE" 
       cmd.Parmeters.Add("@TYPE", SqlDbType.NVarChar, 15).Value = product_type_combox.Text 
      End If 

      If product_name_combox.Text <> "all" Then 
       cmd.CommandText += " AND PRO_NAME = @NAME" 
       cmd.Parmeters.Add("@Name", SqlDbType.NVarChar, 60).Value = product_name_combox.Text 
      End If 

      If embossing_top_combox.Text <> "all" Then 
       cmd.CommandText += " AND EMBOSS_TOP = @EMBOSS_TOP" 
       cmd.Parameters.Add("@EMBOSS_TOP", SqlDbType.NVarChar, 20).Value = embossing_top_combox.Text 
      End If 

      If embossing_bottom_combox.Text <> "all" Then 
       cmd.CommandText += " AND EMBOSS_BOTTOM = @EMBOSS_BOTTOM" 
       cmd.Parameters.Add("@EMBOSS_BOTTOM", SqlDbType.NVarChar, 20).Value = embossing_top_combox.Text 
      End If 

      If line_number_combox.Text <> "all" Then 
       cmd.CommandText += " AND LINE_NO = @LINE_NO" 
       cmd.Parameters.Add("@LINE_NO", SqlDbtype.Int).Value = Integer.Parse(line_number_combox.Text) 
      End If 

      If shift_search_combox.Text <> "all" Then 
       cmd.CommandText += " AND SHIFT = @SHIFT" 
       cmd.Parameters.Add("@SHIFT", SqlDbType.NVarChar, 10).Value = shift_search_combox.Text 
      End If 

      'This should probably be a RANGE of thicknesses, just like the dates. 
      If std_thickness_combox.Text <> "all" Then 
       cmd.CommandText += " AND STD_THICK = @STAND_THICKNESS" 
       cmd.Parameters.Add("@STAND_THICKNESS", SqlDbType.Float).Value = Double.Parse(std_thickness_combox.Text) 
      End If 

      If color_search_combox.Text <> "all" Then 
       cmd.CommandText += " AND COLOR = @COLOR" 
       cmd.Parameters.Add("@COLOR", SqlDbType.NVarChar, 15).Value = color_search_combox.Text 
      End If 

      If Not String.IsNullOrWhiteSpace(FROMTIME) THEN 
       cmd.CommandText += " AND PRO_DATE >= @FROMTIME" 
       cmd.Parameters.Add("@FROMTIME", SqlDbType.DateTime).Value = DateTime.Parse(FROMTIME) 
      End If 

      If Not String.IsNullOrWhiteSpace(TOTIME) THEN 
       cmd.CommandText += " AND PRO_DATE < @TOTIME" 
       cmd.Parameters.Add("@TOTIME", SqlDbType.DateTime).Value = DateTime.Parse(TOTIME) 
      End If 

      Dim dataadapter As New SqlDataAdapter(cmd) 
      Dim ds As New System.Data.DataSet() 
      dataadapter.Fill(ds, "PRODUCT") 
     End Using 

     With Me.DataGridView1 
      .RowsDefaultCellStyle.BackColor = Color.AliceBlue 
      .AlternatingRowsDefaultCellStyle.BackColor = Color.White 
     End With 

     DataGridView1.DataSource = ds.Tables(0) 
     DataGridView1.AutoGenerateColumns = False 

    Catch ex As Exception 
     MessageBox.Show(ex.ToString) 
    End Try 
End Sub 

现在解释为什么你第二次没有得到结果。运行此方法时，你这样做：

DataGridView1.Columns.Clear() 

但是你也这样做：

DataGridView1.AutoGenerateColumns = False 

这第一个片段删除任何列在设置之前，无论是代码或由设计师。你第一次没事，因为你可以自动生成列。但通过第二次，您已将此设置为False。现在，您没有为网格和定义的列，您告诉它不要自动生成它们。因此你看不到任何结果。