浅析Ajax后台success传来json数据的问题

$.ajax({ 
type: "post", 
url: "Default.aspx", 
dataType: "json", 
success: function (data) { 
$("input#showTime").val(data[0].demoData); 
}, 
error: function (XMLHttpRequest, textStatus, errorThrown) { 
alert(errorThrown); 
} 
});

Response.Clear(); 
Response.Write("[{\"demoData\":\"This Is The JSON Data\"}]"); 
Response.Flush(); 
Response.End();

$.ajax({ 
type: "post", 
url: "JqueryCSMethodForm.asmx/GetDemoData", 
dataType: "json",/*这句可用可不用，没有影响*/ 
contentType: "application/json; charset=utf-8", 
success: function (data) { 
$("input#showTime").val(eval('(' + data.d + ')')[0].demoData); 
//这里有两种对数据的转换方式，两处理方式的效果一样 
//$("input#showTime").val(eval(data.d)[0].demoData); 
}, 
error: function (XMLHttpRequest, textStatus, errorThrown) { 
alert(errorThrown); 
} 
});

public static string GetDemoData() { 
return "[{\"demoData\":\"This Is The JSON Data\"}]"; 
}

success:function(data){ 
eval(data); 
}