Regex for Month Number

This is the regular expressions pattern I use to test whether string characters represent a month number (from 01 to 12):

(0[1-9]|1[0-2])

The expression part inside the brackets is broken into 2 possible parts divided by a vertical bar (or pipe symbol): 0[1-9] or 1[0-2].

If a string matches any of the 2 parts it is true.

The first one says that the 2-character string has to start with 0 and end with any number in the range from 1 to 9, e.g. 01, 02, 09

The second part matches any 2-character string that starts with 1 and ends with 0, 1 or 2, i.e. 10, 11, or 12

Delete Contents of IsolatedStorageFile

The easiest way to delete contents of an IsolatedStorageFile is to open it in the Truncate mode:

IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForAssembly();

IsolatedStorageFileStream isoFile = new IsolatedStorageFileStream(myFileName, FileMode.Truncate, isoStore);

According to the MSDN , if a file is opened in the Truncate mode its size should be 0 bytes.

Delete ScriptManager History

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

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

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

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

The post is moved to this blog.