Sys.WebForms.PageRequestManagerServerErrorException: The provider did not return a ProviderManifest instance.
Could not determine storage version; a valid storage connection or a version hint is required.
中文 :
存放區更新、插入或刪除陳述式影響到非預期數目的資料列 (0)。這些實體載入之後可能被修改或刪除了。請重新整理 ObjectStateManager 實體。
英文 :
Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.
@Html.HiddenFor(model => model.CompanyID)
public static class ExtensionMethods
{
public static int ToInt(this String str)
{
return Convert.ToInt32(str);
}
}
protected void Page_Load(object sender, EventArgs e)
{
using (AdventureWorksEntities awe = new AdventureWorksEntities())
{
string s = "1";
var select = from p in awe.ProductModel
where p.ProductModelID == s.ToInt()
select p;
Response.Write(select.Count());
}
}
很無奈，你會得到錯誤訊息:LINQ to Entities 無法辨識方法 'Int32 ToInt(System.String)' 方法，而且這個方法無法轉譯成存放區運算式。
System.NotSupportedException: LINQ to Entities does not recognize the method 'Int32 ToInt(System.String)' method, and this method cannot be translated into a store expression.
protected void Page_Load(object sender, EventArgs e)
{
using (AdventureWorksEntities awe = new AdventureWorksEntities())
{
object obj = "abcd";
var select = from p in awe.ProductModel
where p.CatalogDescription.Contains(obj.ToString())
select p;
Response.Write(select.Count());
//錯誤訊息:LINQ to Entities 無法辨識方法 'System.String ToString()' 方法，
//而且這個方法無法轉譯成存放區運算式。
}
}
protected void Page_Load(object sender, EventArgs e)
{
using (AdventureWorksEntities awe = new AdventureWorksEntities())
{
object obj = "abcd";
var select = from p in awe.ProductModel
where p.CatalogDescription.Contains(Convert.ToString(obj))
select p;
Response.Write(select.Count());
//錯誤訊息:LINQ to Entities 無法辨識方法 'System.String ToString(System.Object)' 方法，
//而且這個方法無法轉譯成存放區運算式。
}
}
NotSupportedException Message=Server-generated keys and server-generated values are not supported by SQL Server Compact.
SQL Server Compact does not support entities with server-generated keys or values when it is used with the Entity Framework. When using the Entity Framework, an entity’s keys may be marked as server generated. This enables the database to generate a value for the key on insertion or entity creation. Additionally, zero or more properties of an entity may be marked as server-generated values. For more information, see the Store Generated Pattern topic in the Entity Framework documentation. SQL Server Compact does not support entities with server-generated keys or values when it is used with the Entity Framework, although the Entity Framework allows you to define entity types with server-generated keys or values. Data manipulation operation on an entity that has server-generated values throws a "Not supported" exception.
private void cbAccount_SelectionChanged(object sender, SelectionChangedEventArgs e) {
dataEntities de = new dataEntities(EntityConn);
Guid guid = new Guid(cbAccount.SelectedValue.ToString());
var select = from val in de.account_value where val.account_id.Equals(guid) select val;
foreach (account_value v in select) { Console.WriteLine(v.value); }
}
與被隕石擊中的機率比較的話，已知一個人每年被隕石擊中的機率估計為170億分之1，等同於在一年內建立數十兆筆UUID並發生一次重複。換句話說，每秒產生10億筆UUID，100年後只產生一次重複的機率是50%。如果地球上每個人都各有6億筆UUID，發生一次重複的機率是50%。