what is the best way to create connection Class in C#

Question

I have windows form that asking user name, password and databaseName, and the way I am using to connect database open to SQL injection!. I want to create different class for my connection string, also want to use get and set methods if it is necessary. what is the best way to do that?

Thanks?

my Connection String

  string db1 = "Data Source=" + txtDatabase.Text + ";User Id=" + txtUserID.Text.ToUpper() + ";Password=" + txtUserPassword.Text + ";";

Answer 1

connection builder

System.Data.SqlClient.SqlConnectionStringBuilder builder =
  new System.Data.SqlClient.SqlConnectionStringBuilder();
builder["Data Source"] = "(local)";
builder["integrated Security"] = true;
builder["Initial Catalog"] = "AdventureWorks;NewValue=Bad";
Console.WriteLine(builder.ConnectionString);