string connString = @"server=.\sqlexpress;user id=sa;password=123";

SqlConnection myConn = new SqlConnection(connString);

string str = "CREATE DATABASE MyDatabase ON PRIMARY " + "(NAME = MyDatabase_Data, " + "FILENAME ='"+ Application.ExecutablePath+ "\\MyDatabaseData.mdf'," + "SIZE = 3MB, MAXSIZE = 10MB, FILEGROWTH = 10%) " + "LOG ON (NAME = MyDatabase_Log, " + "FILENAME ='"+ Application.ExecutablePath+ "\\MyDatabaseLog.ldf'," + "SIZE = 1MB, " + "MAXSIZE = 5MB, " + "FILEGROWTH = 10%)";
            SqlCommand myCommand = new SqlCommand(str, myConn);
            try
            {
                myConn.Open();
                myCommand.ExecuteNonQuery();

System.Data.SqlClient.SqlException: 对文件 "C:\Documents and Settings\Tansion\桌面 
\create database\WindowsFormsApplication1\WindowsFormsApplication1

\bin\Debug\WindowsFormsApplication1.EXE\MyDatabaseData.mdf" 的目录查找失败，出现操作系统错误  123(文件名、目录名或卷标语法不正确。)。
CREATE DATABASE 失败。无法创建列出的某些文件名。请查看相关错误。
   在 System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean 

breakConnection)
   在 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean 

breakConnection)
   在 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject 

stateObj)
   在 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, 

SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject 

stateObj)
   在 System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean 

async)
   在 System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String 

methodName, Boolean sendToPipe)
   在 System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   在 WindowsFormsApplication1.Form1.button1_Click(Object sender, EventArgs e) 位置 

C:\Documents and Settings\Tansion\桌面\create database\WindowsFormsApplication1

\WindowsFormsApplication1\Form1.cs:行号 55

myCommand.ExecuteNonQuery();