title: How to filter and remove duplicate JSON List?
body: <p>I have a local JSON file as shown below and I load it into my flutter project using "<strong>await rootBundle.loadString(****)</strong>".  I decoded to map as "<strong>Map _mapCompany = jsonDecode(jsonComapany)</strong>" than later assign map to list as "_tmpCompany = _mapComapany["companyBranch"];"</p>
  
  <p>Now I need to use filter to get [companyName] and also I need to remove duplicate [companyName] and load to dropdown button.</p>
  
  <p>I use var "_result = new Collection(_tmpCompany).distinct()" to remove duplicate but how can I assign _result.toList() to List _comapnyName; or to dropdown button?</p>
  
  <p>Once the first dropdown loads I use on change event to load branch list using filter. How can I do that?</p>
  
  <pre><code>{  
     “companyBranch”:[  
        {  
           "companyCode":"1",
           "companyName”:”COMAPANY A”,
           "branchCode”:”855”,
           "branchName”:”BRANCH A1”
        },
        {  
           "companyCode":"1",
           "companyName”:”COMPANY A”,
           "branchCode":"856",
           "branchName”:”BRANCH A2“
        },
        {  
           "companyCode":"10",
           "companyName”:”COMAPNY B”,
           "branchCode":"860",
           "branchName”:”BRANCH B1”
        },
        {  
           "companyCode":"10",
           "companyName”:”COMPANY B”,
           "branchCode":"861",
           "branchName”:”BRANCH B2”
        },
  </code></pre>