Question

从我的代码中可以看出，我绝对是初学者。在查找LINQ to SQL问题的其他类似问题后，我发现自己似乎仍然坚持两个目标。 1）使用来自三个组合框和日期选择器的用户选择的输入添加新条目，以及2）使用来自datagridview的交互更新现有数据库条目。

我的windows表格datagridview显示以下输出

**select b.Date, a.EmployeeName, 
       c.ProjectName, b.Hours
from  dbo.Employees a
left outer join dbo.EmployeeProjectHours b
    on a.EmployeeId = b.EmployeeId
left outer join dbo.Projects c
    on b.ProjectId = c.ProjectId**

这是我的ADD方法，用户向我提供了ProjectName，EmployeeName，Date和Hours。对外行人的任何想法都会受到赞赏。

运行插入时没有出错，但是我的dab也没有添加任何内容

     using (ProjectHoursDataContext dbInsert = new ProjectHoursDataContext())
     {
        this.Validate();

        EmployeeProjectHour empHours = new EmployeeProjectHour();

        empHours.Date = dateDateTimePicker.Value;
        empHours.Hours = Convert.ToDecimal(hoursComboBox.Text);
        empHours.ProjectId = dbInsert.Projects.First(p => p.ProjectName == projectNameComboBox.Text).ProjectId;
        empHours.EmployeeId = dbInsert.Employees.First(m => m.EmployeeName == employeeNameComboBox.Text).EmployeeId;

        db.EmployeeProjectHours.InsertOnSubmit(empHours);
        dbInsert.SubmitChanges();

     }

这是我的更新尝试直接从datagridview使用更新。我收到以下错误： System.Windows.Forms.dll中出现'System.ArgumentException'类型的第一次机会异常

     using (ProjectHoursDataContext dbUpdate = new ProjectHoursDataContext())
     {
        this.Validate();
        dataGridView1.AutoGenerateColumns = true;
        projectBindingSource.DataSource = dbUpdate;
        projectBindingSource.DataMember = "Updates";

        projectBindingSource.EndEdit();
        dbUpdate.SubmitChanges();
     }

Answer 1

我最好的猜测到目前为止，您想要修改和更改现有的Employee，Project和EmployeeProjectHours记录。

所以你会这样做：

 using (ProjectHoursDataContext dbInsert = new ProjectHoursDataContext())
 {
    this.Validate();

    // Get the records
    Employee emp = new Employee();
    Project proj = new Project();
    EmployeeProjectHour empHours = new EmployeeProjectHour();

    // Set new values to Employees tables
    emp = dbInsert.Employees
       .First(m => m.EmployeeName == employeeNameComboBox.Text);
    //just get the empployee

    //setting values will update it    
    emp.EmployeeName = employeeNameComboBox.Text;

    // GET an existing project
    proj = dbInsert.Projects
                  .First(p => p.ProjectName == projectNameComboBox.Text);

    //update its values.  
    proj.ProjectName = projectNameComboBox.Text;
    proj.ProjectDescription = "Test";

    //GET an empHours
     empHours = dbInsert.Projects.First(p => p.EmployeeId == emp.EmployeeId && 
                          p.ProjectId == proj.ProjectId);
    //set its values
    empHours.Date = dateDateTimePicker.Value;
    empHours.Hours = Convert.ToDecimal(hoursComboBox.Text);

    dbInsert.SubmitChanges();
 }

Answer 2

除了下面的新代码，我还将项目数据库的增量状态设置为NO。我从之前的stackoverflow讨论中得到了肯定。感谢

  public void AddInfo()
  {
     db.Connection.Open();

        this.Validate();

        EmployeeProjectHour empHours = new EmployeeProjectHour();

        empHours.Date = dateDateTimePicker.Value;
        empHours.Hours = Convert.ToDecimal(hoursComboBox.Text);
        empHours.ProjectId = db.Projects.First(p => p.ProjectName == projectNameComboBox.Text).ProjectId;
        empHours.EmployeeId = db.Employees.First(m => m.EmployeeName == employeeNameComboBox.Text).EmployeeId;

        db.EmployeeProjectHours.InsertOnSubmit(empHours);
        db.SubmitChanges();
        db.Connection.Close();

  }

Linq to SQL ADD和Update

2 个答案: