C# 处理实体框架中的异常 4
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Handle exceptions in entity framework 4
提问by Cristiano Coelho
I need a way to distinguish between SQL exceptions using entity framework LINQ, for example how to distinguish foreing key constraint violation, or unique constraint violation when all i get from the DbUpdateException is a ton of nested inner exceptions and useless long error messages? Are there any lower level exceptions where i can do something like "Catch FKException"; catch "uniqueException" or something like that.
我需要一种使用实体框架 LINQ 来区分 SQL 异常的方法，例如，当我从 DbUpdateException 获得的只是大量嵌套的内部异常和无用的长错误消息时，如何区分前键约束违规或唯一约束违规？是否有任何较低级别的异常，我可以执行诸如“Catch FKException”之类的操作；捕获“uniqueException”或类似的东西。
采纳答案by Cristiano Coelho
Using sql error codes...
使用sql错误代码...
catch (DbUpdateException ex)
{
var sqlex = ex.InnerException.InnerException as SqlException;
if (sqlex != null)
{
switch (sqlex.Number)
{
case 547: throw new ExNoExisteUsuario("No existe usuario destino."); //FK exception
case 2627:
case 2601:
throw new ExYaExisteConexion("Ya existe la conexion."); //primary key exception
default: throw sqlex; //otra excepcion que no controlo.
}
}
throw ex;
}
回答by Mr.LamYahoo
try
{
//code
}
catch (System.Data.Entity.Validation.DbEntityValidationException e)
{
string rs = "";
foreach (var eve in e.EntityValidationErrors)
{
rs = string.Format("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:", eve.Entry.Entity.GetType().Name, eve.Entry.State);
Console.WriteLine(rs);
foreach (var ve in eve.ValidationErrors)
{
rs += "<br />" + string.Format("- Property: \"{0}\", Error: \"{1}\"", ve.PropertyName, ve.ErrorMessage);
}
}
throw new Exception(rs);
}
回答by y?s??la
I wrote couple utility methods for this:
我为此编写了几个实用方法：
public static class DbUtils
{
/// <summary>
/// Takes a code block that updates database, runs it and catches db exceptions. If the caught
/// exception is one of those that are ok to ignore (okToIgnoreChecks) then no
/// exception is raised and result is returned. Otherwise an exception is rethrown.
///
/// This function is intended to be run within an explicit transaction, i.e.:
/// using (var transaction = db.Database.BeginTransaction()), which should be committed/rolledback afterwards.
/// Otherwise, if you don't use a transaction discard the db context or in other words make this operation
/// the only one that you run within implicit transaction.
///
/// This function can wrap a single DB statement, but it's more efficient to wrap multiple statements
/// so that locks are held for shorter period of time.
/// If an exception occurs within a transaction and is caught by this function, all other changes
/// will be still saved to DB on commit if transaction is used.
/// </summary>
/// <typeparam name="T">Any result returned by the code block</typeparam>
/// <param name="context">Database connection</param>
/// <param name="dbCodeBlock">
/// Code block to execute that updates DB. It's expected, but not critical that
/// this code does not throw any other exceptions. Do not call SaveChanges() from the code block itself. Let this
/// function do it for you.
/// </param>
/// <param name="okToIgnoreChecks">
/// List of functions that will check if an exception can be ignored.
/// </param>
/// <returns>Returns number of rows affected in DB and result produced by the code block</returns>
public static Tuple<int, T> IgnoreErrors<T>(DbContext context,
Func<T> dbCodeBlock, params Func<DbUpdateException, bool>[] okToIgnoreChecks)
{
var result = dbCodeBlock();
try
{
var rowsAffected = context.SaveChanges();
return Tuple.Create(rowsAffected, result);
}
catch (DbUpdateException e)
{
if (okToIgnoreChecks.Any(check => check(e)))
return Tuple.Create(0, result);
throw;
}
}
public static bool IsDuplicateInsertError(DbUpdateException e)
{
return GetErrorCode(e) == 2601;
}
public static bool IsForeignKeyError(DbUpdateException e)
{
return GetErrorCode(e) == 547;
}
public static T UpdateEntity<T>(DbContext context, T entity, Action<T> entityModifications)
where T : class
{
return EntityCrud(context, entity, (db, e) =>
{
db.Attach(e);
entityModifications(e);
return e;
});
}
public static T DeleteEntity<T>(DbContext context, T entity)
where T : class
{
return EntityCrud(context, entity, (db, e) => db.Remove(e));
}
public static T InsertEntity<T>(DbContext context, T entity)
where T : class
{
return EntityCrud(context, entity, (db, e) => db.Add(e));
}
public static T EntityCrud<T>(DbContext context, T entity, Func<DbSet<T>, T, T> crudAction)
where T : class
{
return crudAction(context.Set<T>(), entity);
}
}
Here is how you can use it. Example of inserting a potentially duplicate row:
这是您如何使用它。插入潜在重复行的示例：
DbUtils.IgnoreErrors(_db, () => DbUtils.InsertEntity(_db, someEntity),
DbUtils.IsDuplicateInsertError);
No exception will be thrown.
不会抛出任何异常。
Similar to previous example, but handle FK violation exception explicitly:
与前面的示例类似，但显式处理 FK 违规异常：
try
{
var numInserted = DbUtils.IgnoreErrors(_db, () => DbUtils.InsertEntity(_db, someEntity), DbUtils.IsDuplicateInsertError).Item1;
// no FK exception, but maybe unique index violation, safe
// to keep going with transaction
}
catch (DbUpdateException e)
{
if (DbUtils.IsForeignKeyError(e))
{
// you know what to do
}
throw; // rethrow other db errors
}
Eventually you can call commit transaction if you have an explicit transaction, otherwise save has been called on context already.
最终，如果您有显式事务，则可以调用 commit 事务，否则已经在上下文中调用了 save。
