C# and ASP.NET Code

Delete ScriptManager History

2011-12-02T11:17:00.001-08:00

Well, I have not found a way to clear ScriptManager history proper, but the workaround is to use the AddHistoryPoint method and set the value of your property to "0":

ScriptManager1.AddHistoryPoint("myKey", "0");

Check if GridView Column Exists

2011-10-25T10:59:00.000-07:00

If you have a DataRowView you can use the following extension method to check if a GridView column exists:

public static bool ColumnExists( this DataRowView rowData, string fldToCheck)
{
return rowData.Row.Table.Columns.Contains(fldToCheck);
}

Normally, you would use it on RowDataBound event, e.g:

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
DataRowView rowData = e.Row.DataItem as DataRowView;
string fldToCheck = "MyFieldName";
if (e.Row.RowType == DataControlRowType.DataRow)
{
if (rowData.ColumnExists(fldToCheck) ...

Modify Query String

2011-10-17T13:58:00.000-07:00

If you build a hyperlink on a web page dynamically, sometimes you may need to append or modify an existing query string.
To modify a url with an existing query string, first grab the AbsoluteUrl property:

string path = Request.Url.AbsolutePath ;

This will give you a url wihout the query string portion.

If you need to reuse an existing portion of the query string, you have to get it yourself, e.g:

string key = Request.QueryString["key"];
string path = Request.Url.AbsolutePath + "?key="+ key;

Now, you can build your url:

string url = path+ "&key2="+ myValue;

Find GridView Column Index

2011-10-13T13:21:00.000-07:00

If you create GridView columns dynamically using the AutogenerateColumns = true feature, sometimes you need to find a column index from the column name.

I created an extension method to find a column index:

public static int GetIndex(this DataRowView tableData, string fieldName)
        {
            DataColumn dc = tableData.DataView.Table.Columns[fieldName];
            
            if (dc != null)
            {
                return dc.Ordinal;
            }
            return -1;
        }

This is how you call from the RowDataBound event handler:

DataRowView tableData = e.Row.DataItem as DataRowView;
int pos = tableData.GetIndex("MyFieldName");                
if (pos != -1){
   //do your thing
}

WPF GridView Cell Borders

2011-07-27T13:26:00.000-07:00

If you populate a GridView programmatically, and you want to set its style, it's not obvious.

The best approach I found is to set its style in XAML first, and then assign it in code. For example, this is how you would put borders under each row:

<ListView.Resources>
<Style x:Key="itemstyle" TargetType="{x:Type ListViewItem}">
<Setter Property="BorderThickness" Value="1" />
<Setter Property="BorderBrush" Value="#BABABE" />
</Style>
</ListView.Resources>

Then, after you set the DataContext property in code, use:


myListView.ItemContainerStyle = (Style)myListView.Resources["itemstyle"];

Check QueryString for Null

2011-03-17T07:24:00.000-07:00

If you need to determine whether the Request.QueryString is null and take some action depending on the result, it is not enough to check for null. QueryString is an HttpValueCollection type, so even if the Request.Url does not have a query string appended to it, the value of the collection is not going to be null. The proper way to check if the query string contains anything is to check for null and the Count property as well:



if(Request.QueryString!= null && Request.QueryString.Count>0){

     //some piece of code.

}

C# Delegates as Method Parameters

2010-12-03T12:35:00.000-08:00

Let's say you have 2 methods that go through similar steps:

public string GetPrevItem()
 {
    if (IsValidPrevEntry())
    {
        string item = GetPrevString();
        SetProperties();
         return item;
    }
   else
       return null;
 }


public string GetNextItem()
{
    if (IsValidNextEntry())
     {
        string item = GetNextString();
        SetProperties();
        return item;
     }
     else
       return null; 
 }
  

These 2 methods essentially do the same thing. First, they check for some condition, and if the condition evaluates to true, they call another method, set some properties, and return a string. We can use C# delegates to refactor these 2 methods into one. Here is how you do it:
Declare 2 delegates whose signature matches the methods we want to replace:

  delegate bool IsValid();
  delegate string GetItem();

Create a method that will use the delegates:

 private string GetMyItem(IsValid isValid, GetItem getItem)
 {
   if (isValid())
   {
        string item = getItem();
         SetEventProperties();
         return item;
   }
   else
       return null;
  }        

An alternative method signature is as follows:

 private string GetNavItem(Func<bool> isValid, Func<string> getItem)

This way we don't have to declare delegates separately.

Now, we can call the new method, passing the methods that we called before refactoring, as parameters:

string strPrev =   GetMyItem(IsValidPrevEntry, GetPrevString);
string strNext =   GetMyItem(IsValidNextEntry, GetNextString);

An interesting discussion of delegates can be found on the stackflow.

Add JavaScript Dynamically to ASP.NET UpdatePanel

2010-11-16T08:45:00.000-08:00

Use the following example:

System.Text.StringBuilder sb = new System.Text.StringBuilder();       
sb.Append(@" var inputs = document.getElementsByTagName('input');                                  for (var i = 0; i < inputs.length; i++) {
         if (inputs[i].type == 'text') {                 
            inputs[i].onkeypress = function (event) {

               event = event || window.event; 

               return myJavaScriptFunction(event);}
           }}"
       );
ScriptManager.RegisterClientScriptBlock (this, this.GetType(), "ajax", sb.ToString(), true);  

What it does is attaches a JavaScript function (defined elsewhere) to each input box on the page on the key press event, and then registers it for use with a control that is inside an UpdatePanel. This could be used for user input validation. The code has been verified in IE and Firefox.

ASP.NET GridView Subclass with Dynamic Footer Totals

2010-11-10T13:28:00.000-08:00

A frequent requirement when using an ASP.NET GridView on a web page is to have a footer with totals for numeric columns in the GridView. Here is a GridView subclass that calculates footer totals dynamically. It requires 3 parameters:

FirstComputedColumnIndex - the for index of the first column in the data set to be computed
FirstVisbleComputedColumnIndex - for the index of the first computed column to be shown
NumberOfComputedColumns - for the number of computed columns.

Here is the class code:

namespace Eric.TotalGrid {

  public partial class GridView : System.Web.UI.WebControls.GridView
    {
        private Indexer footerTotals;
        public int FirstComputedColumnIndex { get; set; }
        public int FirstVisbleComputedColumnIndex { get; set; }
        public int NumberOfComputedColumns { get; set; }     


        protected override void OnLoad(EventArgs e)
        {
            ShowFooter = true;
            base.OnLoad(e);
        }
        protected override void OnInit(EventArgs e)
        {
            footerTotals = new Indexer(NumberOfComputedColumns);
            InitializeComponent();
            base.OnInit(e);
        }


        private void InitializeComponent()
        {
            this.RowDataBound += new GridViewRowEventHandler(this.GridView1_RowDataBound);
        }


        protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {            


            DataRowView tableData = e.Row.DataItem as DataRowView;


            if (e.Row.RowType == DataControlRowType.DataRow)
            {             
                for (int i = FirstComputedColumnIndex; i < (FirstComputedColumnIndex + NumberOfComputedColumns); i++)
                {                
                    if (tableData[i] != DBNull.Value)
                    {
                        decimal result = 0;
                        if (Decimal.TryParse(tableData[i].ToString(), out result))
                        {
                            footerTotals[i - FirstComputedColumnIndex] += result;
                        }
                    }
                }
            }
            else if (e.Row.RowType == DataControlRowType.Footer)
            {
                for (int i = 0; i < NumberOfComputedColumns; i++)
                {
                    if (e.Row.Cells.Count > (i + FirstVisbleComputedColumnIndex))
                        e.Row.Cells[i + FirstVisbleComputedColumnIndex].Text = footerTotals[i].ToString();
                }
            }
        }

} 


The key to this GridView is using an Indexer class that can be accessed like an array. Here is its listing:


class Indexer
        {
            private int _upperLimit;       


            private decimal[] myArray;


            public Indexer(int limit)
            {
                _upperLimit = limit;
                myArray = new decimal[_upperLimit];
            }
            public decimal this[int index]   // Indexer declaration
            {
                get
                {
                    // Check the index limits.
                    if (index < 0 || index >= _upperLimit)
                        return 0;
                    else
                        return myArray[index];
                }
                set
                {
                    if (!(index < 0 || index >= _upperLimit))
                        myArray[index] = value;
                }
            }
        }

The Indexer class can be nested within the GridView subclass.

The last example shows how to use the custom GridView on a ASP.NET web page:
First, use the register tag:
<%@ Register Namespace="Eric.TotalGrid" TagPrefix="x" Assembly="TotalGrid" %>

Then, use it just like any other GridView:

<x:GridView runat="server" ....
FirstComputedColumnIndex="4" FirstVisbleComputedColumnIndex="3" NumberOfComputedColumns="10" >

Set DataRow Values and Other ASP.NET GridView Tips

2010-10-28T08:12:00.000-07:00

You can set DataRow values in two ways:
First, using a column name:
myDataRow["City"]= "London";

Or, using an index:
myDataRow[2] = "London";

Don't use ItemArray property to set values, it won't work.

Set Text Box Width in a GridView Bound Field:

Use ControlStyle properties:

<asp:BoundField... ControlStyle-Width="60px"/>

Change GridViewRow Appearance:

There are different ways to change GridViewRow appearance. The approach I like involves using the GridViewRow Style property. On RowDataBound event use this:

if (e.Row.RowType == DataControlRowType.Footer)
 {                               
     e.Row.Style.Add("color", "#999999");
     e.Row.Style.Add("font-weight", "bold"); 
     ... 
} 

Did you know that you could pass data format string as a parameter to the ToString() method?

For example:

e.Row.Cells[1].Text = iTotal.ToString("F2")

The above format string specifies 2 decimal places in a numeric value.

Simple Linq to Object example without Casting

2010-10-26T09:30:00.000-07:00

I found this discussion related to casting the result of a LINQ query to a static object at http://devlicio.us/blogs/derik_whittaker/archive/2008/02/22/simple-linq-to-object-example-with-casting.aspx. Since it was not possible to post a comment I decided to write a blog entry on my blog.

The example given at the above page gives the following code:

List<Sport > sports = new List <Sport>();
sports.Add(new Sport { SportID = 1, Name = "Sport 1", Description = "Sport Desc 1" });
sports.Add(new Sport { SportID = 2, Name = "Sport 2", Description = "Sport Desc 2" });
sports.Add(new Sport { SportID = 3, Name = "Sport 3", Description = "Sport Desc 3" });
sports.Add(new Sport { SportID = 4, Name = "Sport 4", Description = "Sport Desc 4" });
sports.Add(new Sport { SportID = 5, Name = "Sport 5", Description = "Sport Desc 5" });


var query = from s in sports
         where s.Name == "Sport 2"
         select s;


Sport sport = (Sport)query.First();

I would like to note that you could rewrite the above statements using lambdas:

Sport sport = sports.Where(s => s.Name == "Sport 2").First();

No "casting" is required.

Resize WinForm Controls Automatically

2010-08-03T08:06:00.000-07:00

Let' say you have a form with a ListBox and OK and Cancel buttons.

You want controls to be resized automatically when a form is resized. This is how you can achieve this by using the Anchor property:

Place all controls inside a GroupBox. Set the Anchor and Dock properties

GroupBox properties:
Anchor : Top, Bottom, Left, Right
Dock : None

Buttons properties:
Anchor : Bottom, Right
Dock : None

ListBox properties:
Anchor : Top, Bottom, Left, Right
Dock : None

Save Window Position in Registry

2010-08-03T07:33:00.000-07:00

This is how you could save a Window position in the Registry so that the Window position could be restored next time the Form loads.

Declare the following constant strings:

public const string REGKEY = @"SOFTWARE\MyCompany\MyApp\";

public const string WINWIDTH = "windowWidth";
public const string WINHEIGHT = "windowHeight";

Then, create a key for your application in the Registry.
Declare a RegistryKey variable:
private RegistryKey key;

Use the following method to obtain the key:

public RegistryKey GetKey(string RegKey)
{
            RegistryKey Key = Registry.CurrentUser.OpenSubKey(RegKey, true);
            if (Key == null)
            {
                Key = Registry.CurrentUser.CreateSubKey(RegKey);
            }
            return Key;
}

key = GetKey(REGKEY);

Get window width and height:

int width = Form1.Size.Width;
int height = Form1.Size.Height;

Save window width and height in the registry and close the RegistryKey.

key.SetValue(WINWIDTH, width);
key.SetValue(WINHEIGHT, height);
key.Close(); 

When you load your form, read the values from the registry:
width = Convert.ToInt16 (key.GetValue(WINWIDTH));
height = Convert.ToInt16 (key.GetValue(WINHEIGHT));


Set the new window size:
Form1.Size = new Size(width, height);

Concise Code to Enable/Disable WinForm Controls

2010-07-20T13:31:00.000-07:00

Let's say you have a check box (cb1) on a form that enables a text box (txt1) and disables a listbox (lst1). You can write a statement that shows this dependency on 2 lines:

txt1.Enabled = cb1.Checked;

lst1.Enabled = !cb1.Checked;

This works fine. However, we repeat the reference to the check box state twice.
There is a way to write the above statements on the same line:

lst1.Enabled = !(txt1.Enabled = cb1.Checked);

Looks simple when you get it right. But it took me a few minutes to figure it out.

Examine Columns in ASP.NET Dynamic Data MetaTable

2010-07-16T13:30:00.000-07:00

This is how you get access to all columns in a MetaTable that serves as a data source to your controls like a DetailsView or a GridView. Dynamic Data generates the following code for each ASP.NET page by default:

   protected MetaTable table;


   protected void Page_Load(object sender, EventArgs e)
   {
       table = DetailsDataSource.GetTable();
       Title = table.DisplayName; 
   }

The MetaTable class has a Columns property that returns a collection of MetaColumns for the table. This allows us to enumerate through the collection and check for any custom attributes on table columns:

    
   foreach (MetaColumn column in table.Columns) 
   {
      if (column.Attributes.OfType<MyCustomAttribute>().Count() > 0)
          ......
      }
   } 

This is based on a tip found at this blog.

Reverse .NET SortedList

2010-07-08T10:39:00.000-07:00

 This post shows how you could reverse a SortedList in C# by its keys:


SortedList<string, string> strlist = new SortedList<string, string>();
strlist.Add("f3", "xxx");
strlist.Add("f1", "ccc");
strlist.Add("f2", "aaa");


foreach (KeyValuePair<string, string> kvp in strlist)
{
    Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}            


Console.WriteLine("reverse the list");
IEnumerable<KeyValuePair<string, string>> revList = strlist.Reverse();
foreach (KeyValuePair<string, string> kvp in revList)
{
    Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}

Open a Text File If It Is Used by Another Process

2010-06-07T12:14:00.000-07:00

Use the FileStream class's Open method to open a file with FileShare.ReadWrite as a parameter. Then use StreamReader class supplying the FileStream object as a constructor argument:

FileStream fs = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
StreamReader sr = new StreamReader(fs);

Set Instance Property Value through Reflection

2010-06-03T06:48:00.000-07:00

This is how you can set object property value using reflection:

Employee emp = new Employee();

PropertyInfo pi = emp.GetType().GetProperty("myPropertyName");
pi.SetValue(emp, "myValue", null);

This is how you read a value:

string value = pi.GetValue(emp, null);

To access all properties of an object:

foreach (PropertyInfo info in emp.GetType().GetProperties()){

    ....

}

Using reflection you can automatically populate a transfer object from a database record if the object property names and types are the same as the record names and types.

An example using a DataReader:

List <employee>list = new List <employee>(); 

while (dataReader.Read())

{

Employee emp = new Employee();

foreach (PropertyInfo info in emp.GetType().GetProperties())

{

   if (!DBNull.Value.Equals(dr[info.Name]))

      info.SetValue(emp, dr[info.Name], null); 

} 

list.Add(emp);

}

The resulting list will hold Employee records.

Object Class Names of the The Authorization Service

2010-06-02T05:52:00.000-07:00

The IAuthorizationService interface exposes two methods you can use to obtain object class names available in TFS.

The first one is ListObjectClasses. It returns a string array of IDs of all defined object classes :

CSS_NODE
EVENT_SUBSCRIPTION
ITERATION_NODE
NAMESPACE
PROJECT

The other one is ListObjectClassActions. You need to supply an object class id as a string parameter to the method. It will return a string array of actions defined for a specified class. For example, if you supply CSS_NODE as a parameter, it will return the following action ids:

GENERIC_READ
GENERIC_WRITE
CREATE_CHILDREN
DELETE
WORK_ITEM_READ
WORK_ITEM_WRITE

Query Operator First

2010-06-01T08:46:00.000-07:00

Let's say you have the following method that returns a FileInfo object from an array if the Name property equals a certain value:

public static FileInfo FindFile(FileInfo[] fileInfoArray, string name)
{            
    foreach (FileInfo fi in fileInfoArray)
    {
        if (fi.Name == name)
            return fi;
    }
    return null;
}

You can replace this method with a call to the query operator First :

FileInfo fileInfo = fileInfoArray.First(fi => fi.Name =="myFileName.txt"); 

Since the query operator First returns a single value, it forces immediate query evaluation.

Replace foreach with Extension Methods and Lambda Expressions

2010-05-27T08:25:00.000-07:00

I suppose many of us use the foreach statement very often in our code. I'll show you how to replace simple foreach statements with new lambda expressions.

Suppose you want to create a List < string> of names of files residing in a directory. This is how you could do it.

Set up an array of FileInfo objects:

string filePath = @"C:\Temp";

DirectoryInfo dInfo = new DirectoryInfo(filePath); 

FileInfo[] fileInfoArray = dInfo.GetFiles();

Create a string type List:

List<string> fileList = new List<string>();

foreach (FileInfo fi in fileInfoArray)

{

    fileList.Add(fi.Name);

}

Select

Using lambda expressions and the Select extension method it is possible to re-write the last 3 lines as follows:

var files = fileInfoArray.Select(fi => fi.Name);

That's one line instead of 3. But we still want a List <string> object to be used later in the code. We need to use the Enumerable.ToList <TSource> method to cast to a List. This is how we do it:

List<string> fileList2 = fileInfoArray.Select(fi => fi.Name).ToList ();  

This way you use one line of code instead of 4.

Where

Now, what if we add only those file names to the List that meet certain criteria, e.g:

foreach (FileInfo fi in fileInfoArray)

{

    if (fi.Length > 10000000)

    {

        largeFiles.Add(fi.Name);

    }

}

Which equivalent extension method can we use to achieve the same result? We need to use the Where extension method of the IEnumerable <T> interface first, and then append the earlier Select method to the statement:

var varLargeFiles =  fileInfoArray.Where (fi => fi.Length > 1000000).Select(fi=>fi.Name);

LINQ

Now, to complete the example, I'll show the way to obtain a similar list using the LINQ:

var q = from fi in fileInfoArray

        where fi.Length > 1000000

        select fi.Name;

List<string> largeFiles2 = q.ToList();

Query operator ToList forces immediate query evaluation.

Boolean Methods

What if you have a method that loops through an array and returns a bool type depending on some condition inside the loop. Can we use query operators instead? It is slightly more difficult but still possible.

Suppose you have the following methods that compares each character in a string array to each character in another string array and returns false when a character in the second array is not found in the first array:

public static bool IsAnagram(string word, string input)

{

    char[] inputArray = input.ToCharArray();

    foreach (char ch in word.ToCharArray())

    {

        if (!inputArray.Contains(ch))

              return false;

    }

    return true;

}

To emulate similar statements, first we need to find the first non-matching character:

char c =  word.ToCharArray().FirstOrDefault (x => !inputArray.Contains(x));    

       

We use the FirstOrDefault operator instead of First because otherwise we may have "Sequence contains no matching element" error if the expression does not returns any characters.

Now we can return a bool value depending on the result of the previous statement:

return (c != 0) ? false: true;

For sheer fun you can rewrite those two statements as follows:

return (word.ToCharArray().FirstOrDefault(x => !inputArray.Contains(x))) == 0;

Sorting

This does not really belong in this post, however, here is a quick way to sort a list of objects. Your object could be similar to this one:

class MyObject{
   public string Symbol {get;set;}
   public double Value {get;set;}
}

myList.Sort((a, b) => a.Symbol.CompareTo(b.Symbol));

Get TFS Team Project Names

2010-05-20T12:42:00.000-07:00

Here is a method that returns a List of names of team projects available at Team Foundation Server

public static List<string> GetProjects(TeamFoundationServer tfsServer) 
        {
            List <string> listProjects = new List<string>();       


            ICommonStructureService iss = (ICommonStructureService)tfsServer.GetService(typeof(ICommonStructureService));            
            ProjectInfo[] projectInfo = iss.ListProjects();


            foreach (ProjectInfo pi in projectInfo)
            {
                listProjects.Add (pi.Name);
            }                                                 


            return listProjects;
        }

Some Registry Methods

2010-05-13T10:31:00.000-07:00

Here are a couple of helper methods to work with Windows Registry:
The first method makes sure you get a reference to a registry subkey. If it does not exist it creates one first. The second one is a preferred way to read a registry value.

 public static RegistryKey GetKey(string RegKey)
 {
     RegistryKey Key = Registry.CurrentUser.OpenSubKey(RegKey, true);


     if (Key == null)
     {
         Key = Registry.CurrentUser.CreateSubKey(RegKey);
     }
     return Key;
}


public static string ReadRegistryValue(RegistryKey key, string regValName)
{
     string[] values = key.GetValueNames();
     if (values.Contains(regValName))
          return key.GetValue(regValName).ToString();
     else
          return String.Empty;
}

Header Cell with CheckBox in DataGridView

2010-02-25T09:52:00.000-08:00

This is my version of a class that displays a check box in a DataGridView Header cell.
This is based on the code from http://social.msdn.microsoft.com/Forums/en-US/winformsdatacontrols/thread/827907ea-c529-4254-9b15-2e6d571f5c5b

It assumes that the check box is located in the first DataGridView column. It allows for column caption and provides built-in check/uncheck functionality. Play with x and y parameters to place the checkbox where you want in the header cell.

Here is a usage example:

DataGridViewColumn column = new DataGridViewCheckBoxColumn();
CheckBox ckBoxMaster = CheckBoxInHeader.CreateCheckBoxInHeader(column, 12, 4, "     Select All");
DataGridView1.Controls.Add(ckBoxMaster);

The class listing:

  class CheckBoxInHeader
    {
    public static CheckBox CreateCheckBoxInHeader(DataGridViewColumn column, int x, int y, string caption)
    {
        CheckBoxInHeader cbInHeader = new CheckBoxInHeader();
        CheckBox ckBox = cbInHeader.CreateCheckBox(column, x, y, caption);
        ckBox.CheckedChanged += new EventHandler(cbInHeader.ckBox_CheckedChanged);
        return ckBox;
    }


    private CheckBox CreateCheckBox(DataGridViewColumn column, int x, int y, string caption)
    {
        CheckBox ckBox = new CheckBox();
        //Get the column header cell bounds           
        Rectangle rect = column.DataGridView.GetCellDisplayRectangle(0, -1, true);
        ckBox.Size = new Size(18, 18);
        //play with check box position
        rect.Offset(x, y);
        //Change the location of the CheckBox to make it stay on the header
        ckBox.Location = rect.Location;
        column.Name = caption;
        return ckBox;
    }


    private void ckBox_CheckedChanged(object sender, EventArgs e)
    {
        CheckBox cb = sender as CheckBox;
        DataGridView dgv = (DataGridView)cb.Parent;


        foreach (DataGridViewRow row in dgv.Rows)
        {

            row.Cells[0].Value = cb.Checked;
        }
    }
    }

Double-Click to Close WinForm ListBox

2010-02-18T12:49:00.000-08:00

If you have a ListBox on a WinForm, and you want the double-click on a selected item to close the form, you need to create a handler for the ListBox double click event.
In the handling method, use the following code:

 private void listBox1_DoubleClick(object sender, EventArgs e)
        {
        if (listBox1.SelectedItem != null)
        {
            listBox1.FindForm().DialogResult = DialogResult.OK;
        }
        }

or, you could use a generic version of the above code:

 ListBox listBox = sender as ListBox ;
       if (listBox.SelectedItem != null)
       {
       listBox.FindForm().DialogResult = DialogResult.OK;
       } 