在Power Apps中使用环境变量

Posted 2022-03-07 luoyong0201

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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=0/>
      <condition attribute=statecode operator=eq value=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);

);

在Cloud Flow中可以直接引用环境变量的值，不需要查询，这个比较方便。