I am getting this runtime exception
Unable to cast object of type 'System.Data.SqlTypes.SqlDecimal' to
type 'System.String'.
How can I fix my code to get my result without exceptions?
ProductsDataContext db = new ProductsDataContext();
var matchedproduct = db.GetTable<product>().SingleOrDefault(p =>p.ProductID==productID);
if (matchedproduct != null)
product.ProductName = txtpname.Text;
db.SubmitChanges();
If you aren't getting a compile time error its because your dbml doesn't accurately depict the column in your database. Your object thinks its a string but its clearly a decimal in the database. You should update it in the dbml editor. Then when you set product name you will have to parse out the decimal value from the Text.
Related
Its just a simple Linq to Entity update query i tried with the following code but it doesn't update the "User" column in the DB.
Its not even throwing any exception also,please some one point me what am missing here.
MyEntities db = new MyEntities ();
var query = from SEVTs in db.SEVTs
where SESID == "4747747"
select SEVTs;
foreach (var SEVTs in query) {
SEVTs.USER = "Test";
}
db.SaveChanges();
Quite interesting, when i try the follwing query in the sql server its not update the record
update Schedwin.SEVT
set
USER3='Test'
Where
SESID='4747747' // here i pass the value as a string
SESID data type is CHAR and its a primary key. if i pass the value as SESID=4747747 then it update that record.
Please ignore my question.
Here what i missed my input value SESID == "4747747" //this have whitespace that's why it didn't updated that particular record.
Thanks All
You are nor modifying SEVTs.USER, but some local variable.
(BTW: create a context in a using construct)
I'm working with an xml document in C# that has multiple (100+) points of stock market data. I'd like to create objects and add them to a List<> by passing initialization values retrieved from an xml document via linq. At the moment I'm just able to run a linq query and return one of the xml fields, in the code below, the attribute "symbol." I'd also like to return the document's "LastTradeDate, DaysLow, DaysHigh, LastTradePriceOnly, Open, and Volume." From there, my custom constructor is: StockDataPoint(Symbol, TradeDate, Open, High, Low, Close, Volume). A nudge in the right direction would be great. Here's the current linq:
var makeInfo =
from s in doc.Descendants("quote")
where s.Element("LastTradeDate") != null
&& s.Attribute("symbol") != null
let dateStr = s.Element("LastTradeDate").Value
where !string.IsNullOrEmpty(dateStr)
&& DateTime.Parse(dateStr, enUS) == targetDate
select s.Attribute("symbol").Value;
Well it depends on your XML format, but you might just want something like:
...
select new StockDataPoint((string) s.Attribute("symbol"),
(DateTime) s.Attribute("TradeDate"),
(decimal) s.Attribute("Open"),
(decimal) s.Attribute("High"),
(decimal) s.Attribute("Low"),
(decimal) s.Attribute("Close"),
(long) s.Attribute("Volume"));
Note that by use the explicit operators on XAttribute, you can avoid performing the parse yourself. Indeed, you can use this earlier in your query too:
var makeInfo = from s in doc.Descendants("quote")
where s.Attribute("symbol") &&
(DateTime?) s.Attribute("LastTradeDate") == targetDate
select ...
If the target of the cast is a nullable type (either a nullable value type or a reference type) then if the attribute is missing, the result will be the null value for that type, which is very handy.
You need to create a class:
select new YourClass {
Symbol = s.Attribute("symbol").Value,
...
}
I'm trying to use an Oracle database with ado.net, and it is proving a painful experience. I use Oracle Client (Oracle.Data namespaces).
The following query runs fine from a query window:
UPDATE PRINT_ARGUMENT
SET VALUE = 'Started'
WHERE REQUEST_ID = 1 AND KEYWORD = '{7D066C95-D4D8-441b-AC26-0F4C292A2BE3}'
When I create an OracleCommand however the same thing blows up with ORA-01722. I can't figure out why.
var cmd = cnx.CreateCommand();
cmd.CommandText = #"
UPDATE PRINT_ARGUMENT
SET VALUE = :value
WHERE REQUEST_ID = :requestID AND KEYWORD = :key";
cmd.Parameters.Add(new OracleParameter("requestID", (long)1);
cmd.Parameters.Add(new OracleParameter("key", "{7D066C95-D4D8-441b-AC26-0F4C292A2BE3}");
cmd.Parameters.Add(new OracleParameter("value", "Started");
cnx.Open();
try { int affected = cnx.ExecuteNonQuery(); }
finally { cnx.Close(); }
When I inspect the command in the debugger, the parameters appear to have mapped to the correct types: requestID has OracleDbType.Int64, key and value are both OracleDbType.Varchar2. The values of the parameters are also correct.
This gets even stranger when you consider that I have other queries that operate on the exact same columns (requestID, keyword, value) using the same approach - and they work without a hiccup.
For the record, the column types are requestID NUMBER(10,0); key VARCHAR2(30); value VARCHAR2(2000).
According to Oracle, ORA-01722 'invalid number' means a string failed to convert to a number. Neither of my string values are numbers, neither of the OracleParameters created for them are numeric, and neither
By default, ODP.NET binds parameters by position, not by name, even if they have actual names in the SQL (instead of just ?). So, you are actually binding requestID to :value, key to :requestID and value to :key.
Correct the order of cmd.Parameters.Add in your code, or use BindByName to tell ODP.NET to use the parameter names.
Since you are using named parameters, you have to tell the Oracle client about it. Otherwise your parameters are mixed up (key is assigned to :value):
OracleParameter parameter = new OracleParameter("requestID", (long)1);
parameter.BindByName = true;
cmd.Parameters.Add(parameter);
It's a strange and unexpected behavior, but that's how it is.
Hi I been searching for my error but I can't find anything that help me. The problem is this. I been working with Subsonic 3, Newtonsoft Json and the linq way of write so I have this easy query:
var found = from client in newclients.All() where client.Period == "sometext" select client;
string periodoJSON = JsonConvert.SerializeObject(periodoFound); //this get "Self referencing loop Exception"
the problem is when I run this script I get the horrible exception "Self referening loop exception" in the JsonConvert line, subsonic have all the objects without any problem but if I do the following.
var found = from client in newclients.All() where client.Period == "sometext" select new client{client.Name, client.LastName, etc};
string periodoJSON = JsonConvert.SerializeObject(periodoFound);
I get the object serialize with a any problem with all the properties. I'm doing the last way because I have to finish my work but is any other way or solution for this problem, if not I will have to write all the properties every time I want to get a full table properties.
hope any can solve my problem o help me in the path for find a solution....
what I have is a really basic query with linq and I try the three values for JsonSerializerSettings and any work, again I'm working with subsonic 3 this not happend either with subsnoic 2 and I can make it work if I specify one by one the properties of the object in the linq query does any have any clue of what is happend, ANY more help would be great!!! If I put the value of Serialize my page get crazy and in a infinity loop state, if I decide for error simple doesn't work and Ignore nothing happen... some more information about this self referencia loop?
var u = usuario.SingleOrDefault(x => x.TipoUsuario == "A" || x.TipoUsuario == "W");
JsonSerializerSettings setting = new JsonSerializerSettings();
setting.ReferenceLoopHandling = ReferenceLoopHandling.Error; //.Serialize .Ignore
Page.ClientScript.RegisterClientScriptBlock(this.GetType(),"usuario", "var usuario=" + JsonConvert.SerializeObject(u, Formatting.None, setting) + ";");
Update ------
I code the following
string jsU = JsonConvert.SerializeObject(u,Formatting.None,new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects, ReferenceLoopHandling = ReferenceLoopHandling.Ignore });
and is workign but the only thing wrongs is that in the json object comes all the information about the columns of subsonic 3 and a BIG chunk of text explain it... does any one know how to not SEND this part of the object??
Without knowing more about you object model it is hard to provide a definitive answer, but I would take a look at the ReferenceLoopHandling enum.
You're calling string SerializeObject(object value) on JsonConvert. Try the string SerializeObject(object value, Formatting formatting, JsonSerializerSettings settings) method instead. The JsonSerializerSettings settings parameter lets you set a bunch of things, including the ReferenceLoopHandling ReferenceLoopHandling { get; set; } property.
You can try these values:
public enum ReferenceLoopHandling
{
Error,
Ignore,
Serialize
}
Obviously, Error is the default and that's what you're getting. Perhaps one of the others will help.
I'm using a Typed DataSet with an Insert statement; I have a table that has a smalldatetime field defined to accept null values. When I insert from a .NET 2.0 FormView, I get a "SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM."
Now, I've read this post, and the parameter as sent to the class constructor is defined as
global::System.Nullable<global::System.DateTime> DoB
So, it looks like it should accept a Nullable obj. Additionally, the generated code is testing the value sent.
if ((DoB.HasValue == true)) {
command.Parameters[6].Value = ((System.DateTime)(DoB.Value));
}
else {
command.Parameters[6].Value = global::System.DBNull.Value;
}
Specifically, the error is occurring when generated SqlClient.SqlCommand.ExecuteScalar() runs:
try {
returnValue = command.ExecuteScalar();
}
So, I guess my question is: how do I use a Typed DataSet to set a blank value (passed from a FormView on CommandName=Insert) to a null in a database?
Ok, so here's what worked for me. First, to reiterate, I've got a Typed DataSet with DataAdapters that's generating the ADO objects. So, on my page, I can create a ObjectDataSource with the type that points to my adapter, and then name the different access methods housed there-in.
No, I have an Insert to a table where basically all the columns are nullable; some varchar, some smalldatetime.
When I submit an empty form, I'd like nulls to be entered. They're not and lots of various errors are thrown. What I ended up doing is subclassing the ObjectDataSource to gain access to the Inserting event. (subclassed for reusability) In the Inserting event, I looped through the InputParameters, and if it was a string and == "", I set it to null. Also, you cannot set ConvertNullToDBNull to true; that causes the strings to fail. This successfully allowed the Nullable to remain null.