尝试 ^ ]您需要使用的语法.

Try here[^] for the SQL syntax you need to use.

String connString =
   "Data Source=bla bla bla; Integrated Security=True;";

Use this code in in the form load 

using (SqlConnection sqlConn = new SqlConnection (connString))
   {
   sqlConn.Open();
   DataTable tblDatabases = sqlConn.GetSchema ("Databases");
   sqlConn.Close();

   foreach (DataRow row in tblDatabases.Rows)
   {
      //add each database to dropdown
   }
}

下拉菜单1的clicked事件
获取选定的项目或数据库名称.
然后针对所选数据库

clicked event of dropdown 1
get the selected item or database name.
then for the selected database

string connString = "Datasource = (selected databasse from dropdown ) integrated securtity = true";

DataTable tables = new DataTable("Tables");
using (SqlConnection sqlConn =       new SqlConnection(connString))
{
    SqlCommand cmd = sqlConn.CreateCommand();
    cmd.CommandText = "select table_name as Name from              INFORMATION_SCHEMA.Tables where TABLE_TYPE =              'BASE TABLE'";
    sqlConn.Open();
    tables.Load(cmd.ExecuteReader(                    CommandBehavior.CloseConnection));
}

可以帮助您..

That will help you out..

入门指南，介绍如何通过C#访问SQL Server [CP的[ ^ ]文章可能帮助您.

Beginners guide to accessing SQL Server through C#[^] article from CP might help you.