C# 如何在C语言中获取Javascript变量值

我有两张长/宽的桌子，每张桌子有1000行。我想使用GoogleMapAPI计算两个纬度/经度之间的距离，并将距离存储在DB中。 代码运行良好，但关键是如何从javascript返回计算出的距离。我尝试使用隐藏字段来存储距离，因为我在页面加载中编写了以下代码，但它不起作用：

        SqlConnection sql_con = new SqlConnection("Database=myDB;Server=mySever;User Id=myID;password=PWD");
        SqlCommand sql_cmd = new SqlCommand("select Zip,Latitude,Longitude from ZipCodes", sql_con);
        SqlDataAdapter sql_adt = new SqlDataAdapter(sql_cmd);
        DataSet dsZip = new DataSet();
        sql_adt.Fill(dsZip);

        sql_cmd = new SqlCommand("select * from MyPlaceLatLong", sql_con);
        sql_adt = new SqlDataAdapter(sql_cmd);
        DataSet dsStore = new DataSet();
        sql_adt.Fill(dsStore);

        for (int zcnt = 0; zcnt < dsZip.Tables[0].Rows.Count; zcnt++)
        {
            for (int i = 0; i < dsStore.Tables[0].Rows.Count; i++)
            {
                Page.ClientScript.RegisterClientScriptBlock(GetType(), "myScssript", "<script>" +
                 "var origin1 = new google.maps.LatLng("+dsZip.Tables[0].Rows[zcnt]["Latitude"].ToString()+","+ dsZip.Tables[0].Rows[zcnt]["Longitude"].ToString()+");" +
                 "var origin2 = new google.maps.LatLng(" + dsStore.Tables[0].Rows[i]["lat"].ToString() + "," + dsStore.Tables[0].Rows[i]["long"].ToString() + ");" +
                  //"var origin1 = new google.maps.LatLng(55.930385, -3.118425);" +
                  //"var origin2 = new google.maps.LatLng(51.483061, -0.004151);" +
                 "var service = new google.maps.DistanceMatrixService();" +
                 " alert('Made it to calculateDistances');" +
                 "service.getDistanceMatrix(" +
                 "{" +
                   "origins: [origin1]," +
                   "destinations: [origin2]," +
                   "travelMode: google.maps.TravelMode.DRIVING," +
                   "unitSystem: google.maps.UnitSystem.IMPERIAL," +
                   "avoidHighways: false," +
                   "avoidTolls: false" +
                 "}, callback);" +
                 "function callback(response, status)" +
                   "{" +
                    "if (status == google.maps.DistanceMatrixStatus.OK) { " +
                    "var origins = response.originAddresses;   " +
                    "var destinations = response.destinationAddresses;" +
                    "for (var i = 0; i < origins.length; i++) {" +
                    "var results = response.rows[i].elements;" +
                    "for (var j = 0; j < results.length; j++) {" +
                    "var element = results[j];" +
                    "var distance = element.distance.text;" +
                    "var duration = element.duration.text; " +
                    "var from = origins[i];" +
                    "var to = destinations[j];" +
                   "alert('The distance:'+ distance);" +
                    "}}}}" +
               "</script>");



            }
        }

---

您需要在JavaScript中设置隐藏字段的值，我不相信我在那里看到了。在ASP中声明字段，如下所示：

<input type="hidden" id="txtDistance" runat="server" />

然后在您的C代码中，您可以这样访问该值：

string cDistance = txtDistance.Value;

//原始文本为字符串cDistance=txtdestance.value

---

希望有帮助

这就是我成功使用的方法

为了提供更多细节，我基于标准WebBrowser编写了一个类。在这个类中，我添加了以下方法：

/// <summary>
/// Execute and get the returned value from the JavaScript into HTML page without appending it.
/// </summary>
/// <param name="strJS">JavaScript to execute.</param>
/// <returns>Dynamic result depending on JavaScript function code.</returns>
public dynamic JSExecuteAndReturnVal(string strJS)
{
    dynamic dynResult = Document.InvokeScript("eval", new[] { strJS });

    return dynResult;
}

诀窍是使用结构化对象返回值。在C代码方面，您确实需要记住这一点，以便正确地获得返回的值

---

使用此示例，您不需要在任何网页中隐藏任何HTML对象，然后从任何JavaScript函数中获取结果。

当我执行最后一行，获取txtdestance.value时，我在WinForm app中发现一个错误：对象引用未设置为对象的实例。

/// <summary>
/// Execute and get the returned value from the JavaScript into HTML page without appending it.
/// </summary>
/// <param name="strJS">JavaScript to execute.</param>
/// <returns>Dynamic result depending on JavaScript function code.</returns>
public dynamic JSExecuteAndReturnVal(string strJS)
{
    dynamic dynResult = Document.InvokeScript("eval", new[] { strJS });

    return dynResult;
}

string strClassName = "whatever";
string strJS = "function JSDoIt(){objResult = document.getElementsByClassName('" + strClassName + "')[0]." +
"textContent; return { Result: objResult }; }; JSDoIt();";
dynamic dynJSResult = myWebBrowser.JSExecuteAndReturnVal(strJS);
decimal.TryParse(dynJSResult.Result.ToString(), out decimal nTotal);