Question

嗨所以我有这个列表，我目前正在使用组合框，这就是为什么我idcategoria = 0与nomeCategoria = "Select your Category"的原因，因此组合框默认项目将是＆＃34;选择你的类别＆＃34 ;. 这是列表的代码

Public Shared Function ObterTodosC() As List(Of Ccategoria)
    Dim lstTodos As List(Of Ccategoria) = New List(Of Ccategoria)

    Dim p As Ccategoria = New Ccategoria()
    p.IdCategoria = 0
    p.NomeCategoria = "select your category"
    lstTodos.Add(p)

    Try
        Using con As SqlConnection = New SqlConnection()

            con.ConnectionString = myDAC._connectionString
            Using cmd As SqlCommand = con.CreateCommand()

                cmd.CommandText = "select * from Categoria"
                con.Open()
                Dim dr As SqlDataReader = cmd.ExecuteReader()
                While dr.Read()
                    Dim p As Ccategoria = New Ccategoria()
                    p.IdCategoria = dr.GetInt32(0)
                    p.NomeCategoria = dr.GetString(1)
                    lstTodos.Add(p)
                End While
            End Using
        End Using
    Catch ex As SqlException
        Throw ex
    Catch ex As Exception
        Throw ex
    End Try
    Return lstTodos
End Function

现在我想在datagridview上使用相同的列表，我想知道是否有一种方法不在datagridview上显示id = 0，或者我是否必须为datagridview创建另一个没有idCategorie = 0的列表，对此有何看法？感谢

Answer 1

从已加载的

创建另一个列表

Dim newList = lstTodos.Skip(1).ToList()

Skip方法将返回没有第一项的新集合请注意，只有- Select your Category -项是列表中的第一项时，此方法才有效。

或者将您的方法更改为不带- Select your Category -项目的返回列表，并仅在需要时添加。

Public Shared Iterator Function ObterTodosC() As IEnumerable(Of Ccategoria)
    Using con As SqlConnection = New SqlConnection()

        con.ConnectionString = myDAC._connectionString
        Using cmd As SqlCommand = con.CreateCommand()

            cmd.CommandText = "select * from Categoria"
            con.Open()
            Dim reader As SqlDataReader = cmd.ExecuteReader()

            While reader.Read()
                Yield New Ccategoria With
                {
                    .IdCategoria = reader.GetInt32(0),
                    .NomeCategoria = reader.GetString(1)
                } 
            End While
        End Using
    End Using
End Function

然后，您可以为datagridview

创建类别列表

Dim forDataGridView = ObterTodosC().ToList()

Dim notSelectedCategory As New Ccategoria With
{
    .IdCategoria = 0,
    .NomeCategoria = "select your category"
}  
Dim forComboBox = forDataGridView.ToList()
forComboBox.Insert(0, notSelectedCategory)

使用此方法可以从ObterTodosC方法中删除副作用所以方法责任只是从数据库加载项目

datagridview没有显示第一行vb.net

1 个答案: