Author: Dee Dubs

Add “Please select” message to databound dropdown list c#

So you have dropdown lists, populated with data from your data storage solution.  You need to prepend the lists with messages such as “Please select an option”.

 

 public void addMessageToDropdown(DropDownList whatDropdown, string ddmessage)
 {
    DropDownList list = whatDropdown as DropDownList;
    if(list != null)
    {
      list.Items.Insert(0, ddmessage);
    }
 
 }

 

Add years to dropdown

Need a dropdown list with some years in it and a custom message as the first choice? How about this to start with: current year through 6 years into the future. Add a dropdownlist control to the page and call this function on pageload.

public void addYearsToDropdown(DropDownList whatDropdown, string ddmessage)
 {
      DropDownList list = whatDropdown as DropDownList;
      if(list != null)
      {
          list.Items.Insert(0, ddmessage);
      }
      int curYear = System.DateTime.Now.Year - 1;
      for(int i = 1; i < 6; i++)
      {
          list.Items.Insert(i, (curYear + i).ToString());
       }
 }

addMessageToDropdown(DropDownListYears, “–Select A Year–“);

Firewall and Web application security

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Checking boxes in a C# ASP checkbox list using values from a database

Suppose you have an ASP checkbox list and you need to check the boxes using data returned from the information storage.

You have a couple of ways the data could have been stored. If each checkbox option is a separate field in the database, you could go with a simple loop, but if they have been stored in one field, you need to put some programming power into it.

Here’s a scenario. I have a “seasons” checklist. There are values stored in the db that the user selected. For example if they chose Summer and Fall, the db string “seasons” would contain “Summer Fall”.

<asp:CheckBoxList ID="CheckBoxListSeasons" runat="server">
 <asp:ListItem>Summer</asp:ListItem>
 <asp:ListItem>Fall</asp:ListItem>
 <asp:ListItem>Winter</asp:ListItem>
 <asp:ListItem>Spring</asp:ListItem>
 </asp:CheckBoxList>

In order to display the list with the Summer and Fall boxes checked, I would do this:

string seasons = "Summer Fall"
for (int i = 0; i < CheckBoxListSeasons.Items.Count; i++)
 {

if (seasons.Contains(CheckBoxListSeasons.Items[i].Value))
 {

CheckBoxListSeasons.Items[i].Selected = true;
 }
 } // end checkbox loop

 

 

 

Transformation Matrices

Rotate a figure 180 degrees around the origin:

From your original figure, just reverse the polarity of the ordered pairs.

Point A(x,y) will be Point a(-x, -y)

(-6,3) (-3,3) (-2,5) (-2,1) (-6,1) original
(6,-3) (3,-3) (2,-5) (2,-1) (6,-1) rotated 180 degrees around origin.

 

Reflect over y-axis

From the original, reverse the polarity of the x value. Point A(x,y) will become point a(-x,y)

(-6,3) (-3,3) (-2,5) (-2,1) (-6,1) original
(6,3) (3,3) (2,5) (2,1) (6,1) reflected over y axis

 

Rotate 90 degrees counter clockwise around origin

The new position of point M (h, k) will become M’ (k, -h)