how to make SQL server Authentication login function.......

I am making a simple login form, where i can login as SQL Server Authenticatin,  i have 2 textfields username and password for SA = user and password.....and i use a connectionstring.

But when i am steping true the code i get error message saying an object refrence is not set as an object....so i am stucked, can somone guide with this bug...?
public void SQLServerLogin(string connectionString)
        {
            SqlConnection sqlConnection3 = new SqlConnection();
 
            if (connectionString.Length == 0)
            {
                return;
            }
            else
            {
                sqlConnection3.ConnectionString = "Data Source=" + sqlConnection3.DataSource + ";initial catalog=" + sqlConnection3.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text;
 
                SqlCommand Command = new SqlCommand(sqlConnection3.ToString());
                Command.CommandTimeout = 2000;
 
                try
                {
                    Command.Connection.Open();
                    Command.ExecuteNonQuery();
                }
                catch (Exception ex)
                {
                    System.Windows.Forms.MessageBox.Show("Couldnt execute the query! " + ex.Message.ToString());
                }
                finally
                {
                    if (Command != null)
                    {
                        Command.Dispose();
                    }
                    if (sqlConnection3 != null)
                    {
                        sqlConnection3.Close();
                        sqlConnection3 = null;
                    }
                }
            }
 
            
        }

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AdnanAsked:
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Jai SConnect With a Mentor Tech ArchCommented:
this is the code that i have to test the connection....

      private bool TestConnection(string DBName)
        {
            try
            {
                SqlConnection conn = new SqlConnection(MakeConnectionString(DBName));
                conn.Open();
                return true;
            }
            catch (Exception ex)
            {
                if (ex.Message != "")
                    CommonFunctions.ShowMessage("Error in connection", string.Format("Cannot connect to server {0} - DB {1}", serverCon.cmbServer.Text, serverCon.cmbdbName.Text), MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            return false;
 
        }
 
        private string MakeConnectionString(string DBName)
        {
            string strConString;
            if (DBName == "") DBName = "master";
//for mixed mode
            if (serverCon.optMixed.Checked == true)
                strConString = string.Format("uid ={0};pwd ={1};data source ={2};initial catalog ={3}", serverCon.txtUserName.Text, serverCon.txtPass.Text, serverCon.cmbServer.Text, DBName);
            else
                strConString = string.Format("integrated security=SSPI;data source ={0};initial catalog ={1}", ServerNameVariable, DBName);
 
            return strConString;
        }

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AdnanAuthor Commented:
When i come to line num 18 - 19 i get this error,   try
                                                                              {
                                                                                       Command.Connection.Open();   ERROR!!! object ref....
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AdnanAuthor Commented:
i just want to make a connection to SQL DB to execute a script and so on.....!
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AdnanAuthor Commented:
hi i am getting a error message saying that the server connection serverCon does not exist in current context.... ???
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AdnanAuthor Commented:
I tyried as you saud in your code...



     private bool TestConnection(string DBName)
        {
            SqlConnection conn = new SqlConnection(MakeConnectionString(DBName));
            try
            {
                conn.Open();
                return true;
            }
            catch (Exception ex)
            {
                if (ex.Message != "")
                    MessageBox.Show("Error in connection", string.Format("Cannot connect to server {0} - DB {1}"), MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            return false;

        }
       
        private string MakeConnectionString(string DBName)
        {
            string strConString;
            SqlConnection serverCon = new SqlConnection();
            if (DBName == "") DBName = "master";
            //for mixed mode
            if (serverCon != null)
            {
                strConString = string.Format("Data Source=" + serverCon.DataSource + ";initial catalog=" + serverCon.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text);
            }
            else
            {
                strConString = string.Format("integrated security=SSPI;data source ={0};initial catalog ={1}", serverCon.ServerVersion, DBName);
            }
                return strConString;
        }
is this function correct....????!
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Jai STech ArchCommented:
no its not correct...

in the line
          strConString = string.Format("integrated security=SSPI;data source ={0};initial catalog ={1}", serverCon.ServerVersion, DBName);
   
you have to pass the parameter servercon.serverVersion as your SERVER name...
          strConString = string.Format("integrated security=SSPI;data source ={0};initial catalog ={1}", "your server name goes here", DBName);
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Jai STech ArchCommented:
i thing you have changed the code that i gave...this will give the proper connection string for you


        private string MakeConnectionString(string DBName)
        {
            string strConString;
            if (DBName == "") DBName = "master";
                strConString = string.Format("uid ={0};pwd ={1};data source ={2};initial catalog ={3}", txtUserName.Text, txtPass.Text, "ServerName", DBName);
 
           return strConString;
        }

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weichunglowCommented:
Not sure  if you can get in through, please try to debug, and mouse over the connection object and see what is the connection string been captured by the connection object.

The reason you get the error message is because your connection string is invalid when passed in runtime. If you would like me to help further, please post your connection string that you captured during debugging.
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AdnanAuthor Commented:
hi i captured this connection string during debuging....

uid =sa;pwd =kunfou;data source =ServerName;initial catalog =
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AdnanAuthor Commented:
this connection string look more correct then the last one,  

Data Source=.;initial catalog=AccountMatch;user id=sa;pwd=kunfou

i get this connection string if i use

strConString = string.Format("Data Source=" + sqlConnection.DataSource + ";initial catalog=" + sqlConnection.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text);

**************************Function running now*****************************
 private string MakeConnectionString(string DBName)
        {
            string strConString;
            if (DBName == "") DBName = "master";
            //strConString = string.Format("uid ={0};pwd ={1};data source ={2};initial catalog ={3}", txtUsername.Text, txtPassword.Text, "ServerName", DBName);
            strConString = string.Format("Data Source=" + sqlConnection.DataSource + ";initial catalog=" + sqlConnection.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text);
           
            //string strConString;
            //if (DBName == "")
            //{
            //    DBName = "master";
            //}
            //if (sqlConnection != null)
            //{
            //    strConString = string.Format("Data Source=" + sqlConnection.DataSource + ";initial catalog=" + sqlConnection.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text);
            //}
            //else
            //{
            //    strConString = string.Format("integrated security=SSPI;data source ={0};initial catalog ={1}", sqlConnection.ServerVersion, DBName);
            //}
            return strConString;
        }
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weichunglowCommented:
alright, base on the conn string you provide earlier on, it's clear that you can't connect because you did not specified the database name (means your DBName is blank),

uid =sa;pwd =kunfou;data source =ServerName;initial catalog =

NEXT, if you say you can obtain the connection string from the following code, then I assume your problem is resolved?

strConString = string.Format("Data Source=" + sqlConnection.DataSource + ";initial catalog=" +
sqlConnection.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text);

In fact, I don't see the need to use string.format in this context as you are not actually formatting any string, the following code will do.

strConString = "Data Source=" + sqlConnection.DataSource + ";initial catalog=" +
sqlConnection.Database + ";user id=" + txtUsername.Text + ";pwd=" + txtPassword.Text ;

In addition, it is not a good practice to "hard code" the connection string in a source code, you should try to keep it in a web.config file. For information on how to store connection string in a web.config file, please refer to the following article.

http://msdn.microsoft.com/en-us/library/ms178411.aspx 
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