在Power Apps中使用环境变量

笛里谁知壮士心，沙头空照征人骨。这篇文章主要讲述在Power Apps中使用环境变量相关的知识，希望能为你提供帮助。
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环境变量(environment variable) 大概在 2019年11月开始Preview，可以参考官方博文：??Environment variables available in preview!??? 。最近已经GA了，可以放心使用了，官方文档请参考：??Environment variables available in preview! ?? 。有点很多，官方文档列举的优点如下，我就不翻译了。

No need to manually edit configurable values in a production environment.
Configure one or more variables in one place and reference like a parameter across multiple solution components.
Enter different values while importing solutions to other environments.
Update values without a code change.
Granular level security managed by ??Microsoft Dataverse??.
Unlimited number of variables (max solution size is 29 MB).
Service the definitions and the values independently or together.
Supported by ??SolutionPackager??? and ??DevOps?? tools enable continuous integration and continuous delivery (CI/CD).
Support for localization.
Can be used to control feature flags and other application settings.

如果要创建环境变量，到 make.powerapps.com 中打开的solution中点击New > Environment variable来新建。

可以看到环境变量的新建界面如下，对于稍微复杂一点的数据类型，我很一般喜欢使用 JSON 这种数据类型。

然后程序如何获取环境变量的值呢？我这里列举的代码示例如下：

public static string GetEnvironmentVariableValue(string variableSchemaName, IOrganizationService service, ITracingService tracingService)

if (string.IsNullOrEmpty(variableSchemaName))

throw new InvalidPluginExecutionException("环境变量名称为空,中止查询该变量的值!");

string returnVal = string.Empty;
var fetchXml = string.Format(@"< fetch version=1.0 mapping=logical top=1 no-lock=true>
< entity name=environmentvariabledefinition>
< attribute name=defaultvalue/>
< filter type=and>
< condition attribute=schemaname operator=eq value=https://www.songbingjia.com/android/0/>
< condition attribute=statecode operator=eq value=https://www.songbingjia.com/android/0/>
< /filter>
< link-entity name=environmentvariablevalue from=environmentvariabledefinitionid to=environmentvariabledefinitionid link-type=outer alias=varvalue>
< attribute name=value/>
< /link-entity>
< /entity>
< /fetch> ", variableSchemaName);
var ec = service.RetrieveMultiple(new FetchExpression(fetchXml));
if (ec.Entities.Count > = 1)

if (ec.Entities[0].Contains("varvalue.value"))

returnVal = ec.Entities[0].GetAttributeValue< AliasedValue> ("varvalue.value").Value.ToString();

else

returnVal = ec.Entities[0].GetAttributeValue< string> ("defaultvalue");

tracingService.Trace($"名称为variableSchemaName环境变量的值是returnVal");
return returnVal;

通过javascript同步获取环境变量值版本：

function getClientUrl()
if (typeof GetGlobalContext == "function" & & typeof GetGlobalContext().getClientUrl == "function")
return GetGlobalContext().getClientUrl();
else
return Xrm.Utility.getGlobalContext().getClientUrl();

function getWebAPIPath()
return getClientUrl() + "/api/data/v9.2/";

this.getEnvironmentVariableValueSync = function (variableSchemaName)
/// < summary> 同步获取环境变量的值< /summary>
/// < param name="variableSchemaName" type="String"> 环境变量的名称< /param>
var returnVal = ""; var req = new XMLHttpRequest();
req.open("GET", encodeURI(getWebAPIPath() + "environmentvariabledefinitions?$select=defaultvalue& $expand=environmentvariabledefinition_environmentvariablevalue($select=value)& $filter=schemaname eq " + variableSchemaName + "& $top=1"), false);
req.setRequestHeader("Accept", "application/json");
req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
req.setRequestHeader("OData-MaxVersion", "4.0");
req.setRequestHeader("OData-Version", "4.0");
req.onreadystatechange = function ()
if (this.readyState == 4)
req.onreadystatechange = null; if (this.status == 200)
var respJson = JSON.parse(req.responseText); if (respJson.value.length === 1)
if (respJson.value[0]["environmentvariabledefinition_environmentvariablevalue"] & & respJson.value[0]["environmentvariabledefinition_environmentvariablevalue"].length > = 1)
returnVal = respJson.value[0]["environmentvariabledefinition_environmentvariablevalue"][0].value;
else
returnVal = respJson.value[0].defaultvalue;

;
req.send(); return returnVal;

利用 Xrm.WebApi.retrieveMultipleRecords 的代码示例是：

Xrm.WebApi.retrieveMultipleRecords("environmentvariabledefinition", "?$select=defaultvalue,displayname& $expand=environmentvariabledefinition_environmentvariablevalue($select=value)& $filter=schemaname eq ly_demoev& $top=1").then(function success(result)
if (result.entities.length === 1)
if (result.entities[0]["environmentvariabledefinition_environmentvariablevalue"]
& & result.entities[0]["environmentvariabledefinition_environmentvariablevalue"].length > 0)
console.log("值是" + result.entities[0]["environmentvariabledefinition_environmentvariablevalue"][0].value);
else if (result.entities[0].defaultvalue)
console.log("值是" + result.entities[0].defaultvalue);
else
console.log("环境变量的值是空");

, function (error)
console.log(error.message);

);