Updating A Field Inserts Lots Of Spaces

I have a database setup and the fields setup as nchar(200).

Now, when I update a row using the code below it inserts the text but then seems to fill the rest of the field with spaces. i.e. if the text is only 10 characters, mssql seems to put 190 characters on the end of it to make 200.

 Is there any reason how I can stop this/1 // Create new command
2 comm = new SqlCommand(
3 "UPDATE Pages SET PageBody=@PageBody, " +
4 "PageMetaTitle=@PageMetaTitle, PageMetaDesc=@PageMetaDesc, PageMetaKeywords=@PageMetaKeywords " +
5 "WHERE PageID=@PageID", conn);
6
7 // Add command parameters
8 comm.Parameters.Add("@PageID", System.Data.SqlDbType.Int);
9 comm.Parameters["@PageID"].Value = idTextBox.Text;
10 comm.Parameters.Add("@PageBody", System.Data.SqlDbType.NVarChar);
11 comm.Parameters["@PageBody"].Value = contentTextBox.Text;
12 comm.Parameters.Add("@PageMetaTitle", System.Data.SqlDbType.NVarChar);
13 comm.Parameters["@PageMetaTitle"].Value = titleTextBox.Text;
14 comm.Parameters.Add("@PageMetaDesc", System.Data.SqlDbType.NVarChar);
15 comm.Parameters["@PageMetaDesc"].Value = descriptionTextBox.Text;
16 comm.Parameters.Add("@PageMetaKeywords", System.Data.SqlDbType.NVarChar);
17 comm.Parameters["@PageMetaKeywords"].Value = keywordsTextBox.Text;