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Search found 7 results on 1 pages for 'nullvalue'.

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• codegen:nullValue vs msprop:nullValue

  - by Ken

  Ok, I have datasets that I created way back in 1.1 framework to which we used codegen:nullValue within the XSD to handle null values. However if I open one of these datasets with vs 2005 (i.e. 2.0 framework) and add a column, it removes the codegen setting from the entire xsd but adds in msprop:nullValue However, unlike previous years, I noticed this time the proper property code was NOT over riden from returning the null value specified in codegen as it was doing in the past. Meaning the msprop appears to be creating the proper code behind the scenes (See example). Anyone know of any other differnces? Should I be concerned with deploying a new xsd, WITHOUT the codegen code but instead with the msprop xml? Example: Original creates _ Public Property ParentID() As Integer Get If Me.IsParentIDNull Then Return -1 Else Return CType(Me(Me.tableCompany.ParentIDColumn),Integer) End If End Get Set Me(Me.tableCompany.ParentIDColumn) = value End Set End Property New creates _ Public Property ParentID() As Integer Get If Me.IsParentIDNull Then Return -1 Else Return CType(Me(Me.tableCompany.ParentIDColumn),Integer) End If End Get Set Me(Me.tableCompany.ParentIDColumn) = value End Set End Property BUT is there anything else that might be occuring that I am NOT seeing thus MAKING me re-enter all the codegen settings? THANKS!

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• executing null values records

  - by jjj

  i am trying to execute the records that have TotalTime null value from the table NewTimeAttendance...TotalTime datatype nchar(10) select * from newtimeattendance where TotalTime = 'NULL' ....nothing select * from newtimeattendance where TotalTime = 'null' ....nothing select * from newtimeattendance where TotalTime = 'Null' ....nothing select * from newtimeattendance where TotalTime = null ....nothing select * from newtimeattendance where TotalTime = Null ....nothing select * from newtimeattendance where TotalTime = NULL ....nothing when i select the whole table i can see that there is some NULL TotalTime values..!! it is small select statment ..why doesn't it work ? is there a way (special way ) to execute the 'NULL' with nchar type ?! thanks in advance

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• Creating a Dynamic DataRow for easier DataRow Syntax

  - by Rick Strahl

  I've been thrown back into an older project that uses DataSets and DataRows as their entity storage model. I have several applications internally that I still maintain that run just fine (and I sometimes wonder if this wasn't easier than all this ORM crap we deal with with 'newer' improved technology today - but I disgress) but use this older code. For the most part DataSets/DataTables/DataRows are abstracted away in a pseudo entity model, but in some situations like queries DataTables and DataRows are still surfaced to the business layer. Here's an example. Here's a business object method that runs dynamic query and the code ends up looping over the result set using the ugly DataRow Array syntax:public int UpdateAllSafeTitles() { int result = this.Execute("select pk, title, safetitle from " + Tablename + " where EntryType=1", "TPks"); if (result < 0) return result; result = 0; foreach (DataRow row in this.DataSet.Tables["TPks"].Rows) { string title = row["title"] as string; string safeTitle = row["safeTitle"] as string; int pk = (int)row["pk"]; string newSafeTitle = this.GetSafeTitle(title); if (newSafeTitle != safeTitle) { this.ExecuteNonQuery("update " + this.Tablename + " set safeTitle=@safeTitle where pk=@pk", this.CreateParameter("@safeTitle",newSafeTitle), this.CreateParameter("@pk",pk) ); result++; } } return result; } The problem with looping over DataRow objecs is two fold: The array syntax is tedious to type and not real clear to look at, and explicit casting is required in order to do anything useful with the values. I've highlighted the place where this matters. Using the DynamicDataRow class I'll show in a minute this code can be changed to look like this:public int UpdateAllSafeTitles() { int result = this.Execute("select pk, title, safetitle from " + Tablename + " where EntryType=1", "TPks"); if (result < 0) return result; result = 0; foreach (DataRow row in this.DataSet.Tables["TPks"].Rows) { dynamic entry = new DynamicDataRow(row); string newSafeTitle = this.GetSafeTitle(entry.title); if (newSafeTitle != entry.safeTitle) { this.ExecuteNonQuery("update " + this.Tablename + " set safeTitle=@safeTitle where pk=@pk", this.CreateParameter("@safeTitle",newSafeTitle), this.CreateParameter("@pk",entry.pk) ); result++; } } return result; } The code looks much a bit more natural and describes what's happening a little nicer as well. Well, using the new dynamic features in .NET it's actually quite easy to implement the DynamicDataRow class. Creating your own custom Dynamic Objects .NET 4.0 introduced the Dynamic Language Runtime (DLR) and opened up a whole bunch of new capabilities for .NET applications. The dynamic type is an easy way to avoid Reflection and directly access members of 'dynamic' or 'late bound' objects at runtime. There's a lot of very subtle but extremely useful stuff that dynamic does (especially for COM Interop scenearios) but in its simplest form it often allows you to do away with manual Reflection at runtime. In addition you can create DynamicObject implementations that can perform  custom interception of member accesses and so allow you to provide more natural access to more complex or awkward data structures like the DataRow that I use as an example here. Bascially you can subclass DynamicObject and then implement a few methods (TryGetMember, TrySetMember, TryInvokeMember) to provide the ability to return dynamic results from just about any data structure using simple property/method access. In the code above, I created a custom DynamicDataRow class which inherits from DynamicObject and implements only TryGetMember and TrySetMember. Here's what simple class looks like:/// <summary> /// This class provides an easy way to turn a DataRow /// into a Dynamic object that supports direct property /// access to the DataRow fields. /// /// The class also automatically fixes up DbNull values /// (null into .NET and DbNUll to DataRow) /// </summary> public class DynamicDataRow : DynamicObject { /// <summary> /// Instance of object passed in /// </summary> DataRow DataRow; /// <summary> /// Pass in a DataRow to work off /// </summary> /// <param name="instance"></param> public DynamicDataRow(DataRow dataRow) { DataRow = dataRow; } /// <summary> /// Returns a value from a DataRow items array. /// If the field doesn't exist null is returned. /// DbNull values are turned into .NET nulls. /// /// </summary> /// <param name="binder"></param> /// <param name="result"></param> /// <returns></returns> public override bool TryGetMember(GetMemberBinder binder, out object result) { result = null; try { result = DataRow[binder.Name]; if (result == DBNull.Value) result = null; return true; } catch { } result = null; return false; } /// <summary> /// Property setter implementation tries to retrieve value from instance /// first then into this object /// </summary> /// <param name="binder"></param> /// <param name="value"></param> /// <returns></returns> public override bool TrySetMember(SetMemberBinder binder, object value) { try { if (value == null) value = DBNull.Value; DataRow[binder.Name] = value; return true; } catch {} return false; } } To demonstrate the basic features here's a short test: [TestMethod] [ExpectedException(typeof(RuntimeBinderException))] public void BasicDataRowTests() { DataTable table = new DataTable("table"); table.Columns.Add( new DataColumn() { ColumnName = "Name", DataType=typeof(string) }); table.Columns.Add( new DataColumn() { ColumnName = "Entered", DataType=typeof(DateTime) }); table.Columns.Add(new DataColumn() { ColumnName = "NullValue", DataType = typeof(string) }); DataRow row = table.NewRow(); DateTime now = DateTime.Now; row["Name"] = "Rick"; row["Entered"] = now; row["NullValue"] = null; // converted in DbNull dynamic drow = new DynamicDataRow(row); string name = drow.Name; DateTime entered = drow.Entered; string nulled = drow.NullValue; Assert.AreEqual(name, "Rick"); Assert.AreEqual(entered,now); Assert.IsNull(nulled); // this should throw a RuntimeBinderException Assert.AreEqual(entered,drow.enteredd); } The DynamicDataRow requires a custom constructor that accepts a single parameter that sets the DataRow. Once that's done you can access property values that match the field names. Note that types are automatically converted - no type casting is needed in the code you write. The class also automatically converts DbNulls to regular nulls and vice versa which is something that makes it much easier to deal with data returned from a database. What's cool here isn't so much the functionality - even if I'd prefer to leave DataRow behind ASAP -  but the fact that we can create a dynamic type that uses a DataRow as it's 'DataSource' to serve member values. It's pretty useful feature if you think about it, especially given how little code it takes to implement. By implementing these two simple methods we get to provide two features I was complaining about at the beginning that are missing from the DataRow: Direct Property Syntax Automatic Type Casting so no explicit casts are required Caveats As cool and easy as this functionality is, it's important to understand that it doesn't come for free. The dynamic features in .NET are - well - dynamic. Which means they are essentially evaluated at runtime (late bound). Rather than static typing where everything is compiled and linked by the compiler/linker, member invokations are looked up at runtime and essentially call into your custom code. There's some overhead in this. Direct invocations - the original code I showed - is going to be faster than the equivalent dynamic code. However, in the above code the difference of running the dynamic code and the original data access code was very minor. The loop running over 1500 result records took on average 13ms with the original code and 14ms with the dynamic code. Not exactly a serious performance bottleneck. One thing to remember is that Microsoft optimized the DLR code significantly so that repeated calls to the same operations are routed very efficiently which actually makes for very fast evaluation. The bottom line for performance with dynamic code is: Make sure you test and profile your code if you think that there might be a performance issue. However, in my experience with dynamic types so far performance is pretty good for repeated operations (ie. in loops). While usually a little slower the perf hit is a lot less typically than equivalent Reflection work. Although the code in the second example looks like standard object syntax, dynamic is not static code. It's evaluated at runtime and so there's no type recognition until runtime. This means no Intellisense at development time, and any invalid references that call into 'properties' (ie. fields in the DataRow) that don't exist still cause runtime errors. So in the case of the data row you still get a runtime error if you mistype a column name:// this should throw a RuntimeBinderException Assert.AreEqual(entered,drow.enteredd); Dynamic - Lots of uses The arrival of Dynamic types in .NET has been met with mixed emotions. Die hard .NET developers decry dynamic types as an abomination to the language. After all what dynamic accomplishes goes against all that a static language is supposed to provide. On the other hand there are clearly scenarios when dynamic can make life much easier (COM Interop being one place). Think of the possibilities. What other data structures would you like to expose to a simple property interface rather than some sort of collection or dictionary? And beyond what I showed here you can also implement 'Method missing' behavior on objects with InvokeMember which essentially allows you to create dynamic methods. It's all very flexible and maybe just as important: It's easy to do. There's a lot of power hidden in this seemingly simple interface. Your move…© Rick Strahl, West Wind Technologies, 2005-2011Posted in CSharp  .NET   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Does NULL and nil are equal?

  - by monish

  Hi Guys, Actually my question here is does Null and nil are equal or not? I had an Example but I am confused when they are equal when they are not. NSNull *nullValue = [NSNull null]; NSArray *arrayWithNull = [NSArray arrayWithObject:nullValue]; NSLog(@"arrayWithNull: %@", arrayWithNull); id aValue = [arrayWithNull objectAtIndex:0]; if (aValue == nil) { NSLog(@"equals nil"); } else if (aValue == [NSNull null]) { NSLog(@"equals NSNull instance"); if ([aValue isEqual:nil]) { NSLog(@"isEqual:nil"); } } Here in the above case it shows that both Null and nil are not equal and it displays "equals NSNull instance" NSString *str=NULL; id str1=nil; if(str1 == str) { printf("\n IS EQUAL........"); } else { printf("\n NOT EQUAL........"); } And in the second case it shows both are equal and it displays "IS EQUAL". Anyone's help will be much appreciated. Thank you, Monish.

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• Can a Generic Method handle both Reference and Nullable Value types?

  - by Adam Lassek

  I have a series of Extension methods to help with null-checking on IDataRecord objects, which I'm currently implementing like this: public static int? GetNullableInt32(this IDataRecord dr, int ordinal) { int? nullInt = null; return dr.IsDBNull(ordinal) ? nullInt : dr.GetInt32(ordinal); } public static int? GetNullableInt32(this IDataRecord dr, string fieldname) { int ordinal = dr.GetOrdinal(fieldname); return dr.GetNullableInt32(ordinal); } and so on, for each type I need to deal with. I'd like to reimplement these as a generic method, partly to reduce redundancy and partly to learn how to write generic methods in general. I've written this: public static Nullable<T> GetNullable<T>(this IDataRecord dr, int ordinal) { Nullable<T> nullValue = null; return dr.IsDBNull(ordinal) ? nullValue : (Nullable<T>) dr.GetValue(ordinal); } which works as long as T is a value type, but if T is a reference type it won't. This method would need to return either a Nullable type if T is a value type, and default(T) otherwise. How would I implement this behavior?

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• datagridview apply cellstyle to cells

  - by SchlaWiener

  I used this example to create a DateTime column for a DataGridView in my winforms app. http://msdn.microsoft.com/en-us/library/7tas5c80.aspx I can see the new column in the Windows Forms Designer and add it to an existing DataGridView. However, I want to be able to change the display format when I change the "DefaultCellStyle" within the designer. The designer generated code looks like this: DataGridViewCellStyle1.Format = "t" DataGridViewCellStyle1.NullValue = Nothing Me.colDate.DefaultCellStyle = DataGridViewCellStyle1 Me.colDatum.Name = "colDate" Me.colDatum.Resizable = System.Windows.Forms.DataGridViewTriState.[False] Which is fine. But since the code of the DataGridViewCalendarCell does this in the constructor: Public Sub New() Me.Style.Format = "d" End Sub The format never changes to "t" (time format). I didn't find out how to apply the format from the owning column to I use this woraround atm: Public Overrides Function GetInheritedStyle _ (ByVal inheritedCellStyle As _ System.Windows.Forms.DataGridViewCellStyle, _ ByVal rowIndex As Integer, ByVal includeColors As Boolean) _ As System.Windows.Forms.DataGridViewCellStyle If Me.OwningColumn IsNot Nothing Then Me.Style.Format = Me.OwningColumn.DefaultCellStyle.Format End If Return MyBase.GetInheritedStyle(_ inheritedCellStyle, rowIndex, includeColors) End Function However, since this is just an hack I want to know which is the "how it should" be done way to apply the default cellstyle from a DataGridViewColumn to its cells. Any suggestions?

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• Serialize JavaScript's navigator object

  - by kappa

  Hi, I'm creating a page to help diagnose the problem our users are experiencing with our web pages (you know, asking a user "What browser are you using?" usually leads to "Internet"). This page already submits to me all the HTTP headers and now I'm trying to have JavaScript give some more informations, so I thought it would be great to have the user's navigator JavaScript object and I started looking how to serialize it so I can submit it through a form. The problem is I'm not able to serialize the navigator object using any JSON library I know of, everyone returns an empty object (?!), so I decided to write an ad-hoc serializer. You can find the code here: <!DOCTYPE html> <html> <head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js" type="text/javascript"></script> <script type="text/javascript"> function serialize (object) { var type = typeof object; if (object === null) { return '"nullValue"'; } if (type == 'string' || type === 'number' || type === 'boolean') { return '"' + object + '"'; } else if (type === 'function') { return '"functionValue"'; } else if (type === 'object') { var output = '{'; for (var item in object) { if (item !== 'enabledPlugin') { output += '"' + item + '":' + serialize(object[item]) + ','; } } return output.replace(/\,$/, '') + '}'; } else if (type === 'undefined') { return '"undefinedError"'; } else { return '"unknownTypeError"'; } }; $(document).ready(function () { $('#navigator').text(serialize(navigator)); }); </script> <style type="text/css"> #navigator { font-family: monospaced; } </style> <title>Serialize</title> </head> <body> <h1>Serialize</h1> <p id="navigator"></p> </body> </html> This code seems to work perfectly in Firefox, Opera, Chrome and Safari but (obviously) doesn't work in Internet Explorer (at least version 8.0), it complains that "Property or method not supported by the object" at line for (var item in object) {. Do you have any hint on how to fix the code or how to reach the goal (serialize the navigator object) by other means?

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