I've been struggling with one problem these past few hours.
I keep getting an error and it tells me that the specified cast is not valid. I'm able to change the values on the database using the stored procedure. However, when I try doing it with the executable I get that error.
This is the error
System.InvalidCastException: Specified cast is not valid.
at Administrator_Panel.DB.ReadAccountInfo(String UserID, In32& Count)
This is the code.
public static Account ReadAccountInfo(string UserID, out int Count)
if (Reader.Read())
ReturnValue = new Account((int)Reader["UserUID"],
(string)Reader["Pw"],
(bool)Reader["Admin"],
(bool)Reader["Staff"],
(short)Reader["Status"],
(int)Reader["Point"],
(int)Reader["DaemonPoints"]);
Any help would be appreciated. :) Thank you
See this answer: How to (efficiently) convert (cast?) a SqlDataReader field to its corresponding c# type?
You can't just cast SqlDataReader fields to their corresponding value types because of the possibility of nulls. You can use nullable types but it's likely your Account object isn't setup to take nullable types.
One way you can try to handle this is to add null checking:
ReturnValue = new Account(Reader["UserUID"] == DBNull.Value ? 0 : (int)Reader["UserUID"] ,
Reader["Pw"] == DBNull.Value ? "" : Reader["Pw"].ToString(),
Reader["Admin"] == DBNull.Value ? false : (bool)Reader["Admin"],
Reader["Staff"] == DBNull.Value ? false : (bool)Reader["Staff"],
Reader["Status"] == DBNull.Value ? (short) 0 : (short)Reader["Status"],
Reader["Point"] == DBNull.Value ? 0 : (int)Reader["Point"],
Reader["DaemonPoints"] == DBNull.Value ? 0 : (int)Reader["DaemonPoints"]);
Related
I am selecting information from a database of mostly strings, however I have a datatype of number which if that value in the db is null I would like it to display as blank in my grid. I've tried reading the number in as a string but it is not working.
AccountUid = dr["ACCOUNT_UID"] == DBNull.Value ? null: Convert.ToInt32(dr["ACCOUNT_UID"])
I'm not sure what to put in where null is to get a db value of null to display as nothing. AccountUid is an int?.
Below is how I got it to work. So I was close I just needed to add (int?) to null and it works now.
AccountUid = dr["ACCOUNT_UID"] == DBNull.Value ? (int?)null : Convert.ToInt32(dr["ACCOUNT_UID"])
I have no values to insert into MaxPrice or MinPrice columns which can be null. The values when they don't exist are originally were seen as , , in the resulting Sql expression. I got a syntax error before and changed the code to this
(setItem.MinPrice.ToString()!="")?setItem.MinPrice.ToString() : null,
(setItem.MaxPrice.ToString() != "") ? setItem.MaxPrice.ToString() : null
But when I execute this I get an error and the sql still looks like the , , . The columns are decimal but can be NULL.
Use parameters. Always.
cmd.Parameters.AddWithValue("#minPrice",
setItem.MinPrice == null ? DBNull.Value : (object)setItem.MinPrice);
cmd.Parameters.AddWithValue("#maxPrice",
setItem.MaxPrice == null ? DBNull.Value : (object)setItem.MaxPrice);
or with a tool like Dapper:
// adds "#MinPrice" and "#MaxPrice" correctly as parameters, as long
// as the sql contains those tokens in some way
conn.Execute(sql, new { setItem.MinPrice, setItem.MaxPrice });
The bad fix - do not use - would be to supply the literal "null" in your concatenation. There are many many reasons not to do this:
// bad code; do not use
(setItem.MinPrice.ToString() != "") ? setItem.MinPrice.ToString() : "null",
(setItem.MaxPrice.ToString() != "") ? setItem.MaxPrice.ToString() : "null"
I am trying to populate a combobox with a list my query returns. When I execute my program it gives me a specified cast is not valid error ( I have it execute on page load event). Every field in the database I have to work with can be null except the primary key. So I tried using DBNull.Value but it can't get my (int)reader fields to work. I have supplied my code below for a better understanding. How can I get my (int)reader's to work with my statements, so they can read when there is a null value?
CustData cd = new CustData();
cd.CustomerID = (int)reader["CustomerID"];
cd.Name = reader["Name"] != DBNull.Value ? reader["Name"].ToString() : string.Empty;
cd.ShippingAddress = reader["ShippingAddress"] != DBNull.Value ? reader["ShippingAddress"].ToString() : string.Empty;
cd.ShippingCity = reader["ShippingCity"] != DBNull.Value ? reader["ShippingCity"].ToString() : string.Empty;
cd.ShippingState = reader["ShippingState"] != DBNull.Value ? reader["ShippingState"].ToString() : string.Empty;
cd.ShippingZip = (int)reader["ShippingZip"];
cd.BillingAddress = reader["BillingAddress"] != DBNull.Value ? reader["BillingAddress"].ToString() : string.Empty;
cd.BillingCity = reader["BillingCity"] != DBNull.Value ? reader["BillingCity"].ToString() : string.Empty;
cd.BillingState = reader["BillingState"] != DBNull.Value ? reader["BillingState"].ToString() : string.Empty;
cd.BillingZip = (int)reader["BillingZip"];
cd.Territory = reader["Territory"] != DBNull.Value ? reader["Territory"].ToString() : string.Empty;
cd.Category = reader["Category"] != DBNull.Value ? reader["Category"].ToString() : string.Emptyy
That is because int is not nullable. You need to use int? or nullable<int> (long hand) to allow it to be an int OR a null value.
You can then use the usual .HasValue and .Value etc to get the value from the item.
EDIT: To enhance the visibility of my comment to this answer. I would advise against checking for NULL and storing Zero into your property because then when you save back you are changing a Null to a Zero even though nothing has been changed by the system. Now, reports etc may distinguish between NULL and Zero (very often) and could start doing strange things!
Null does NOT equal zero!! If you assume it does as a work around... What happens if I truly do want to record zero? How do you differentiate between a real zero and a "was null now zero" trick? Do it right, save yourself the pain!
Use nullable int, or just make your control for your int's too
reader["ShippingZip"] != DBNull.Value ? (int)reader["ShippingZip"] : default(int);
You should use a nullable int for your variable and cast it, like (int?). Int can only have a value; nullable types can also be null. When you use a nullable type, you can look at the property .HasValue. Here is the MSDN page: http://msdn.microsoft.com/en-us/library/2cf62fcy.aspx
EnumType = reader["EnumTypeId"] == DBNull.Value ? EnumType.None : (EnumType)(int)reader["EnumTypeId"];
I thought if reader["EnumTypeId"] is null, it should assign the EnumType.None value, but it is still trying to cast the null value to an int which is obviously causing an exception.
I tried the following and it did not work either:
EnumType = reader["EnumTypeId"] == null ? EnumType.None : (EnumType)(int)reader["EnumTypeId"];
Instead of using Enums, I went ahead and decided to use a nullable int, so now my code is slightly different, but it still does not work with DBNull.Value, null, or GetOrdinal...
intType= reader["intType"] == DBNull.Value ? null : (int?)reader["intType"];
Also, why do I have to do a (int?) cast instead of just a (int) cast?
Don't use DBNull, just use plain old null.
EnumType = reader["EnumTypeId"] == null ? EnumType.None : (EnumType)(int)reader["EnumTypeId"];
Edit
The issue could be that the database type of EnumTypeId isn't an int/Int32. If so, then reading as a string and then parsing should fix the problem.
EnumType? enumVal = null;
if (reader["EnumTypeId"] != null)
{
int intVal;
enumVal = (int.TryParse(reader["EnumTypeId"].ToString(), out intVal)) ? (EnumType)intVal : null;
}
EnumType = ? EnumType.None : (EnumType)(int)reader["EnumTypeId"];
Another way you can use is IsDBNull method:
int index = reader.GetOrdinal("EnumTypeId");
EnumType = reader.IsDBNull(index) ? EnumType.None :
(EnumType)reader.GetInt32(index);
I'm creating an object for my database and I found a weird thing, which I don't understand:
I've an object which should reference a "language" by an ID, but this can be null, so my property is a int?(Nullable<int>)
so firstly I tried to use the object initializer:
myObject = new MyObject()
{
myNullableProperty = language == null ? null : language.id;
}
but it doesn't work! It tell me that null cannot be converted to int
But if I it in a if/else structure, I can put null in a var and then assign it to my properties.
Why is this acting like this?
You may try casting the null to int? as the ?: operator requires both operands to return the same type:
myNullableProperty = language == null ? (int?)null : language.id
This is because of a type mismatch. You must cast your null value to the int type.
The reason is, when using the ? operator the left and the right side of the : are required to be from the same type and typeof(null)!=typeof(int) so:
myNullableProperty = language == null ? (int?)null : language.id;
Most likely null is interpreted as object which obviously can't be assigned to int. You might want to use myNullableProperty = language == null ? (int?)null : language.id;