我试图在VB.NET中编写datagrid。我没看到桌子。我在主程序和调用函数中有调用语句： [英] I am trying to write datagrid in VB.NET. I don't see the table. I have the calling statement in the main program and the calling function as:

问题描述

我正在尝试在VB.NET中编写datagrid。我没看到桌子。我在主程序和调用函数中有调用语句：



我尝试过：

如果results.Rows.Count> 1然后
调用GridView1_SelectedIndexChanged（_DogID，_Name，_OwnerID）
结束如果
 
 
 
受保护的子GridView1_SelectedIndexChanged（Id为整数，名称为字符串，所有者作为整数）
 
 Dim dogTags As New DataTable（）
 dogTags.Rows.Add（_DogID，_Name，_OwnerID）
 GridView1.DataSource = dogTags 
 GridView1.DataBind （）
 
结束子

解决方案

原因很明显：每当你摧毁以前的数据时调用程序 GridView1_SelectedIndexChanged 。



移动此行 Dim dogTags As New DataTable（）在程序之外（例如：在 InitializeComponent 方法之后）。

然后用这种方式改变你的程序：

 '  Dim dogTags As New DataTable（） 
 
 受保护的  Sub  GridView1_SelectedIndexChanged（Id  As   Integer ，Name 作为 字符串，所有者作为 整数）
 
  Dim  dt  As  DataTable =  DirectCast （GridView1.DataSource，DataTable）
  Dim  row  As  DataRow = dt.NewRow（）
 ' 不要忘记分别更改列名他们在你的项目中的名字！ 
 row（  DogId）= Id 
行（ 名称）=名称
行（ 所有者）=所有者
 dogTags.Rows.Add（row）
 GridView1.DataSource = dogTags 
 结束  Sub  

与此同时。请阅读：

Visual Basic中的范围| Microsoft Docs [ ^ ]

变量和Microsoft .NET中的方法范围 [ ^ ]

如何：控制变量的范围（Visual Basic）| Microsoft Docs [ ^ ]

DirectCast Operator（Visual Basic）| Microsoft Docs [ ^ ]

如何：添加行到一个DataTable [ ^ ]

I am trying to write datagrid in VB.NET. I don't see the table. I have the calling statement in the main program and the calling function as:

What I have tried:

 If results.Rows.Count > 1 Then
                Call GridView1_SelectedIndexChanged(_DogID, _Name, _OwnerID)
            End If



Protected Sub GridView1_SelectedIndexChanged(Id As Integer, Name As String, Owner As Integer)
        
        Dim dogTags As New DataTable()       
        dogTags.Rows.Add(_DogID, _Name, _OwnerID)
        GridView1.DataSource = dogTags       
        GridView1.DataBind()

    End Sub

解决方案

The reason is obvious: you are destroing previous data every time when you call procedure GridView1_SelectedIndexChanged.

Move this line Dim dogTags As New DataTable() outside the procedure (for example: after InitializeComponent method).
Then change your procedure this way:

'Dim dogTags As New DataTable()       

Protected Sub GridView1_SelectedIndexChanged(Id As Integer, Name As String, Owner As Integer)
        
        Dim dt As DataTable = DirectCast(GridView1.DataSource, DataTable)
        Dim row As DataRow = dt.NewRow()
        'do not forget to change column names respectively to their names in your project!
        row("DogId") = Id
        row("Name") = Name
        row("Owner") = Owner
        dogTags.Rows.Add(row)
        GridView1.DataSource = dogTags       
End Sub

In a meanwhile. please read this:
Scope in Visual Basic | Microsoft Docs[^]
Variable and Method Scope in Microsoft .NET[^]
How to: Control the Scope of a Variable (Visual Basic) | Microsoft Docs[^]
DirectCast Operator (Visual Basic) | Microsoft Docs[^]
How to: Add Rows to a DataTable[^]

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