Writing URLs to link type fields in SharePoint via code can be accomplished by using the SPFieldUrlValue type (C#):
SPFieldUrlValue redirectUrl = new SPFieldUrlValue();
redirectUrl.Url = "http://theServer/app.aspx";
redirectUrl.Description = " Applications";
data.ListItem["Link Field"] = redirectUrl;
data.Update();
Alternatively and more directly (C#):
SPList list = web.Lists["yourlistname"];
SPListItem item = list.Items[0]; //Get the list item
item["Link Field"] = "http://theServer/app.aspx, Applications"; //the first part contains the URL followed by a comma and space, then the URL description
item.Update();
In SharePoint Designer:
First create a string variable (Build Dynamic String action) that contains the URL and link description:
for example “http://theServer/app.aspx, Applications” (like in the first example above).
Then set the link field value equal to the variable.
For email links use the following syntax:
mailto:email@address, Name of Contact
Again note that there must be a comma and a space between the email address and the contact name.