Question

我想使用datagridview中的实体框架将多个项目添加到数据库，但是总是在SaveChanges()方法中出错。

这是我的保存按钮代码

foreach (DataGridViewRow row in SaleGrid.Rows)
{
    var saleProduct = new SaleProduct
    {
        SalesId = Convert.ToInt32(txtInvoice.Text),
        CatId = Convert.ToInt32(row.Cells["CatId"].Value ?? DBNull.Value),
        CatQuiltyId = Convert.ToInt32(row.Cells["QualityId"].Value ?? DBNull.Value),
        SuitDesignId = Convert.ToInt32(row.Cells["DesignId"].Value ?? DBNull.Value),
        SaleType = Convert.ToInt32(row.Cells["TypeId"].Value ?? DBNull.Value),
        StockId = Convert.ToInt32(row.Cells["StockId"].Value ?? DBNull.Value),
        Price = Convert.ToString(row.Cells["Price"].Value ?? DBNull.Value)
    };
    Db.SaleProducts.Add(saleProduct);
    Db.SaveChanges();
}

public partial class SaleProduct
{

    public int Id { get; set; }
    public Nullable<int> SalesId { get; set; }
    public Nullable<int> CatId { get; set; }
    public Nullable<int> CatQuiltyId { get; set; }
    public Nullable<int> SuitDesignId { get; set; }
    public Nullable<int> CustomerId { get; set; }
    public Nullable<int> SaleType { get; set; }
    public Nullable<int> StockId { get; set; }
    public string Price { get; set; }

在EntityFramework.dll中发生了类型为'System.Data.Entity.Validation.DbEntityValidationException'的未处理异常

其他信息：对一个或多个实体的验证失败。有关更多详细信息，请参见“ EntityValidationErrors”属性。

Answer 1

DbNull无法转换为Int32。如果您的值可以为null，则您的媒体资源必须为空。

public MyClass 
{
    public int? NullableProp {get; set;}
}

和您的代码

var saleProduct = new SaleProduct
{
     NullableProp = String.IsNullOrEmpty(txtInvoice.Text) ? (int)null :
          Convert.ToInt32(txtInvoice.Text),
     ....
}

富特莫尔，看来您有ModelValidationError。在这种情况下，您需要检查EntityValidationErrors以了解您的模型到底出了什么问题。

Answer 2

根据您的错误消息，似乎您的某些字段可能已在数据库中设置为NOT NULL，并且您尝试将NULL放入。您可以在VS中的“异常”中检查EntityValidationErrors字段-确切的信息是哪些字段不正确

Answer 3

您必须先检查null

row.Cells["Price"] is null ? DBNull.Value:Convert.ToString(row.Cells["Price"].Value)

Answer 4

使用此代码以及显示消息框时使用
```
 ctrl + c
```
要复制邮件

然后在此处发布

try {

foreach (DataGridViewRow row in SaleGrid.Rows)
{
    var saleProduct = new SaleProduct
    {
        SalesId = Convert.ToInt32(txtInvoice.Text),
        CatId = Convert.ToInt32(row.Cells["CatId"].Value ?? DBNull.Value),
        CatQuiltyId = Convert.ToInt32(row.Cells["QualityId"].Value ?? DBNull.Value),
        SuitDesignId = Convert.ToInt32(row.Cells["DesignId"].Value ?? DBNull.Value),
        SaleType = Convert.ToInt32(row.Cells["TypeId"].Value ?? DBNull.Value),
        StockId = Convert.ToInt32(row.Cells["StockId"].Value ?? DBNull.Value),
        Price = Convert.ToString(row.Cells["Price"].Value ?? DBNull.Value)
    };
    Db.SaleProducts.Add(saleProduct);
    Db.SaveChanges();
}


}
catch (Exception e)
{
  var messages = new List<string>();
  do
  {
    messages.Add(e.Message);
    e = e.InnerException;
  }
  while (e != null) ;
  var message = string.Join(" - ", messages);
  MessageBox.Show(message);

}

使用实体framewrk以c＃Windows形式将多个项目添加到数据库

4 个答案: