如何将数据集对象转换为列表 <string> 在vb.net

Question

我要从数据库返回行的结果集，我想在UI上为HTML控件分配这些值。

我正在从数据库获取数据到DataSet中。

例如，我的数据如下所示：

ID  EmpId    Question    Comments

1    2        abcdefgh   comments1
2    6        xyhgjkjh   comments2
3    6        kjhkjhjk   comments3
4    6        uyyiuyuui  comments4
5    3        erteyeyuy  comments5
6    6        qapooioip  comments6

基于input（EmpId）我获取数据。对于EmpId = 6，我想使用如下HTML字段在UI上显示以上数据：

Q1。 xyhgjkjh

comments2

Q2。 kjhkjhjk

comments3

Q3.uyyiuyuui

comments4

Q4.qapooioip

comments6

我只想通过遍历数据库中的结果集以HTML标签显示。

我正在创建如下属性：

Public class MyClass
{
   public int Id{get;set;}
   public int EmpId{get;set;}
   public String Question{get;set;}
   public String Comments{get;set;}
}

我想使用上面的类，并将结果集值设置为属性，然后遍历它，并分配给UI上的HTML控件。

如何转换数据集并将其设置为MyClass obj属性，并将其分配给VB.NET中的HTML控件。

我需要具有“问题列表”属性吗？

有什么帮助吗？ 提前致谢。

Answer 1

使用您的课程：

' I'm going to assume that the class properties are in the same order as the dataset and that there is only one table in the dataset.

Dim TheClassInstance as MyClass ' Create an instance of the class
Dim MyClassList as List(Of TheClassInstance)
Dim MyDataRow as DataRow
For Each MyDataRow in TheDataSet.Tables(0).Rows
     TheClassInstance = New MyClass 
     TheClassInstance.Id = MyDataRow(0)
     TheClassInstance.EmpId = MyDataRow(1)
     TheClassInstance.Question = MyDataRow(2)
     TheClassInstance.Comments = MyDataRow(3)
     MyClassList.Add(TheClassInstance)
     ' Everytime you loop you're adding an instance of the class to the list
Next

要访问该类的每个实例，您可以使用for每个循环或使用变量作为索引的循环来循环，以获取列表中的数据。 对每个循环使用a：

Dim MyClassInstance as new MyClass
For Each MyClassInstance in MyClassList 
    ' You can set the text property of labels and textbox controls to the data
    Textbox_Comments.text = MyClassInstance.Comments
    ' ... etc
Next

编辑以解决每个父母的多重问题：

更改课程：

Public class MyClass

   Public Property Id as Integer
   Public Property EmpId as Integer
   Public Property Question as List(of String)
   Public Property Comments as String

End Class

我假设每个EmplID都有一个带有EmplId的父表和Questions的子表：

Dim TheClassInstance as MyClass ' Create an instance of the class
Dim MyDataRow as DataRow
Dim MyDataRow2 as DataRow ' For clarity
For Each MyDataRow IN ParentDataSet.Tables(0).Rows
     TheClassInstance = New MyClass 
     TheClassInstance.Id = MyDataRow(0)
     TheClassInstance.EmpId = MyDataRow(1)
     TheClassInstance.Comments = MyDataRow(3)
     Dim MySecondDataSet as Dataset = GetQuestions(MyDataRow(1) ' Get questions for EmplId
     For Each MyDataRow2 in MySecondDataSet.Tables(0).Rows
         ' It's assumed that the question is the only column in the table
         TheClassInstance.Questions.Add(MyDataRow2(0))
     Next
Next

当所有问题都在表格的一行中时：

Dim TheClassInstance as MyClass ' Create an instance of the class
Dim MyDataRow as DataRow
For Each MyDataRow IN ParentDataSet.Tables(0).Rows
     TheClassInstance = New MyClass 
     TheClassInstance.Id = MyDataRow(0)
     TheClassInstance.EmpId = MyDataRow(1)
     TheClassInstance.Comments = MyDataRow(3)
     ' I assume that the questions start in column 4
     ' Add each question in the row, I assume 4 questions in order
     TheClassInstance.Questions.Add(MyDataRow(4))
     TheClassInstance.Questions.Add(MyDataRow(5))
     TheClassInstance.Questions.Add(MyDataRow(6))
     TheClassInstance.Questions.Add(MyDataRow(7))
Next

Answer 2

创建将DataRow转换为类MyClass的方法的另一种方法

Public Function ToMyClass(row As DataRow)
    Return New MyClass With
    {
        .Id = row.Field(Of Integer)("ID"),
        .EmpId = row.Field(Of Integer)("EmpID"),
        .Question = row.Field(Of String)("Question"),
        .Comments = row.Field(Of String)("Comments"),
    }
End Function

通用方法DataRow.Field(Of T)将列值转换为期望的类型，这提供了编译器提供的某种类型安全性-为此，您需要将Option Strict设置为On 。

然后，您将可以在“一行”中创建课程列表

Dim data As DataTable = dataset.Tables(0)
Dim questions As List(Of MyClass) = 
    data.AsEnumerable().Select(AddressOf ToMyClass).ToList()