How to create a login page in C# and database is sqlserver 2005

If this is a windows application, then don't use the term "page" - use "form" instead. "Page" implies a website is involved, which is not the case for windows applications.

The first thing to do is create a database table:

ColumnName   Type
ID           Varies - some like integer, with identity set on. Personally, I prefer GUID.
Username     NVARCHAR - maximum length will depend on you, but 256 is a fair compromise.
Password     VARBINARY(64)

You may need other columns.
You will then need to make a form, with two text boxes: tbUserName and tbPassword - the latter should have the UseSystemPasswordChar property set to true. It will also need two buttons: OK and Cancel.
Then add two public properties:

public string UserName
   {
   get { return tbUserName.Text; }
   set { tbUserName.Text = value; }
   }
public byte[] Password
   {
   get { return GetSHA1(UserName, tbPassword.Text); }
   }

You will find the Method GetSHA1 in this Tip: Password Storage: How to do it.[^] along with an explanation of why to use it.

When the user clicks the OK button, check the username and password against those stored in your DB: I assume you know how to fetch things from SQL. Again, there is a method in the Tip for comparing them.

You will need to add a couple of other forms as well: create user, change password, lost password, delete user are the most common - but if you get the above working they should be pretty easy.