如何使用linq-c將XML元素值轉換爲int＃

Question

我試圖從我的XML元素中獲取值並將其轉換爲使用linq命令的整數，因此我可以使用它來執行一些數學公式。

這是我到目前爲止已經試過：

private void buttonTab4Mod1Calculate_Click(object sender, EventArgs e) 
     { 
      var document = XDocument.Load(workingDir + @"\Level4.xml"); 

      var assessmentOneWeight = from d in document.Descendants("moduleTitle") 
             where d.Value == (String)comboBoxTab4Mod8.SelectedItem 
             select d.Parent.Element("assessmentOneWeight").Value; 
      int a = 0; 
      foreach (var item in assessmentOneWeight) 
      { 
       a = Convert.ToInt32(item); 
      } 
      MessageBox.Show(a.ToString()); 
     } 

但價值仍是0出於某種原因。

這是我的xml文件：

<?xml version="1.0" encoding="utf-8" ?> 
<SoftwareEngineering> 
    <Module> 
    <moduleCode>ECSE401</moduleCode> 
    <moduleTitle>Programming Methodology</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Coursework</assessmentOne> 
    <assessmentOneWeight>40</assessmentOneWeight> 
    <assessmentTwo>Coursework</assessmentTwo> 
    <assessmentTwoWeight>40</assessmentTwoWeight> 
    <assessmentThree>Test</assessmentThree> 
    <assessmentThreeWeight>20</assessmentThreeWeight> 
    </Module> 
    <Module> 
    <moduleCode>ECSC404</moduleCode> 
    <moduleTitle>Computer Systems Fundamentals</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Test1</assessmentOne> 
    <assessmentOneWeight>30</assessmentOneWeight> 
    <assessmentTwo>Test2</assessmentTwo> 
    <assessmentTwoWeight>30</assessmentTwoWeight> 
    <assessmentThree>Test3</assessmentThree> 
    <assessmentThreeWeight>40</assessmentThreeWeight> 
    </Module> 
    <Module> 
    <moduleCode>EBSY401</moduleCode> 
    <moduleTitle>Information and Data Modelling</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Test</assessmentOne> 
    <assessmentOneWeight>25</assessmentOneWeight> 
    <assessmentTwo>Coursework1</assessmentTwo> 
    <assessmentTwoWeight>10</assessmentTwoWeight> 
    <assessmentThree>Coursework2</assessmentThree> 
    <assessmentThreeWeight>35</assessmentThreeWeight> 
    <assessmentFour>Coursework3</assessmentFour> 
    <assessmentFourWeight>30</assessmentFourWeight> 
    </Module> 
    <Module> 
    <moduleCode>ECSC405</moduleCode> 
    <moduleTitle>Software Development Principles</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Test1</assessmentOne> 
    <assessmentOneWeight>30</assessmentOneWeight> 
    <assessmentTwo>Coursework</assessmentTwo> 
    <assessmentTwoWeight>40</assessmentTwoWeight> 
    <assessmentThree>Test2</assessmentThree> 
    <assessmentThreeWeight>30</assessmentThreeWeight> 
    </Module> 
    <Module> 
    <moduleCode>ECSC407</moduleCode> 
    <moduleTitle>Web Technology</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Tutorials</assessmentOne> 
    <assessmentOneWeight>20</assessmentOneWeight> 
    <assessmentTwo>Coursework</assessmentTwo> 
    <assessmentTwoWeight>20</assessmentTwoWeight> 
    <assessmentThree>Exam</assessmentThree> 
    <assessmentThreeWeight>60</assessmentThreeWeight> 
    </Module> 
    <Module> 
    <moduleCode>ECSC409</moduleCode> 
    <moduleTitle>Software Engineering Principles</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Coursework1</assessmentOne> 
    <assessmentOneWeight>40</assessmentOneWeight> 
    <assessmentTwo>Coursework2</assessmentTwo> 
    <assessmentTwoWeight>30</assessmentTwoWeight> 
    <assessmentThree>Coursework3</assessmentThree> 
    <assessmentThreeWeight>30</assessmentThreeWeight> 
    </Module> 
    <Module> 
    <moduleCode>ECSC408</moduleCode> 
    <moduleTitle>Mathematics for Computing</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Coursework</assessmentOne> 
    <assessmentOneWeight>50</assessmentOneWeight> 
    <assessmentTwo>Exam</assessmentTwo> 
    <assessmentTwoWeight>50</assessmentTwoWeight> 
    </Module> 
    <Module> 
    <moduleCode>EBSY400</moduleCode> 
    <moduleTitle>Communication and Learning Skills</moduleTitle> 
    <credits>15</credits> 
    <assessmentOne>Coursework</assessmentOne> 
    <assessmentOneWeight>30</assessmentOneWeight> 
    <assessmentTwo>Coursework</assessmentTwo> 
    <assessmentTwoWeight>70</assessmentTwoWeight> 
    </Module> 
</SoftwareEngineering> 

將不勝感激一些幫助。

Answer 1

只是cast the XElement to int：

private void buttonTab4Mod1Calculate_Click(object sender, EventArgs e) 
{ 
    var document = XDocument.Load(workingDir + @"\Level4.xml"); 

    string selectedItem = (string) comboBoxTab4Mod8.SelectedItem; 
    var assessmentOneWeight = from d in document.Descendants("moduleTitle") 
           where (string) d == selectedItem 
           select (int) d.Parent.Element("assessmentOneWeight"); 
    foreach (int item in assessmentOneWeight) 
    { 
     MessageBox.Show(item.ToString()); 
    }   
} 

注意，當參考確實是XElement，但如果你投一個空引用int?你得到一個空值回你也可以cast to int?它的工作方式相同 - 如果您不知道是否爲對應的元素，這可能會有所幫助。

XElement和XAttribute也有很多明確的轉換 - 它們讓生活變得更容易。

Answer 2

我敢肯定，您的assessmentOneWeight集合不包含單個值，因爲在XML中找不到comboBoxTab4Mod8.SelectedItem的值。

因此，您總是得到0，因爲a使用0進行初始化。

---

順便說一句：我強烈建議你改進你的代碼。

遍歷<Module>元素而不是<moduleTitle>元素。這使得更多的意義，因爲你需要這個元素（即<assessmentOneWeight>）

科協<assessmentOneWeight值的數據>直接在LINQ的語句，像這樣：

var assessmentOneWeight = 
    from d in document.Descendants("moduleTitle") 
    where d.Value == (String)comboBoxTab4Mod8.SelectedItem 
    select int.Parse(d.Parent.Element("assessmentOneWeight").Value); 

你foreach沒有很好地設計，因爲它僅取得集合中找到的最後一個值。如果你真的想要使用LINQ的強大功能並只選擇那個值。