Linq to SQL添加和更新

Question

正如你從我的代碼可以看出，我絕對是一個初學者。在搜索了關於LINQ to SQL問題的其他類似問題之後，我發現自己仍然看起來停留在兩個目標上。 1）添加一個新的條目，其中包含來自三個組合框和日期選擇器的用戶選擇的輸入，以及2）使用datagridview中的交互更新現有數據庫條目。

我的Windows窗體的DataGridView顯示的是下面的輸出

**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** 

這裏是我的add方法向用戶提供我項目名，EmployeeName，日期和時間。任何外行的想法將不勝感激。

我不明白運行插入一個錯誤，但沒有被添加到我的DAB以及

 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(); 

    } 

這裏是我的更新嘗試直接從DataGridView中使用的更新。我得到以下錯誤：類型「System.ArgumentException」的第一次機會異常出現在System.Windows.Forms.dll中

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

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

Answer 1

我最好的猜測到目前爲止，您希望編輯和更改現有的Employee，Project和EmployeeProjectHours記錄。

所以，你會怎麼做：

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

除了下面的新代碼，我也把我的狀態增量爲我的項目數據庫爲NO。我從之前的一個stackoverflow討論中設定了它。謝謝

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(); 

    }