使用C＃访问数据集值

Question

I have a application that calls a web service where GetDataSourceMappingTable its a data structure its a data set .

What I am trying to do its to extract the value of a certain column (Users_Tests) which will give me the mandatory parameter to be able to call another web service GetUser() .

Here you have data set structure:

GetDataTableResponse xmlns="http://tempuri.org/">
         <GetDataTableResult>
            <xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
               <xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:UseCurrentLocale="true">
                  <xs:complexType>
                     <xs:choice minOccurs="0" maxOccurs="unbounded">
                        <xs:element name="Table">
                           <xs:complexType>
                              <xs:sequence>
                                 <xs:element name="SourceID" type="xs:string" minOccurs="0"/>
                                 <xs:element name="Caption" type="xs:string" minOccurs="0"/>
                              </xs:sequence>
                           </xs:complexType>
                        </xs:element>
                     </xs:choice>
                  </xs:complexType>
               </xs:element>
            </xs:schema>

I need to call the element name "Caption" and pass the value Users_Test (where Users_Test its a value inside that table) to get the SourceID eg "Data1"

Here is my code so far:

var ds = proxy.GetDataTable();
var DataSourceId = ds.Tables["Table"].Select("Caption = 'Users_test'");

UserData[] userDataId = client.GetUser(ref apiKey, ref message, DataSourceId.ToString()); //GetUserData need the sourceID e.g. Data1 to be able to be used

Whenever I run the program in the DataSourceId variable inside GetUser() method is not being passed correctly. I get an array 0 and 1. In 0 I get Data1 and in 1 I get Users_tests.

I am suppose to get eg "Data1"

How I can only get the value of the Caption but give the SourceID to the GetUser() method?

As well I would like to be able to have multiple captions such us ( Select("Caption = 'Users_test'"); and Select("Caption = 'Users_test1'"); and Select("Caption = 'Users_test3'");

Is this possible?

Thanks

Answer 1

DataTable.Select() returns a DataRow[] array, so you can use the Linq Select method to project the rows to the entry for Caption . The following expression gets the SourceID value corresponding to your caption, returns null if not found, and throws an exception on multiple matches:

    var DataSourceId = ds.Tables["Table"]
        .Select("Caption = 'Users_test'") // Find rows with Caption = 'Users_test'
        .Select(r => r["SourceID"])       // Project to the value of SourceId
        .Where(s => s != DBNull.Value)    // Filter DBNull (might occur when the SourceID cell is missing
        .Select(s => s.ToString())        // Project to string value
        .SingleOrDefault();               // null if no matches, throw an exception if more than one match.

If you might reasonably expect more than one row with Caption = 'Users_test' , you can loop through them all with a foreach statement:

    var query = ds.Tables["Table"]
        .Select("Caption = 'Users_test'") // Find rows with Caption = 'Users_test'
        .Select(r => r["SourceID"])       // Project to the value of SourceId
        .Where(s => s != DBNull.Value)    // Filter DBNull (might occur when the SourceID cell is missing
        .Select(s => s.ToString());        // Project to string value
    foreach (var DataSourceId in query)
    {
    }

Prototype fiddle .

Update

To select multiple captions with DataTable.Select() , use the OR operator:

            var query = ds.Tables["Table"]
                .Select("Caption = 'Users_test' OR Caption = 'Users_test3'") // Find rows any of several captions
                .Select(r => r["SourceID"])       // Project to the value of SourceId
                .Where(s => s != DBNull.Value)    // Filter DBNull (might occur when the SourceID cell is missing
                .Select(s => s.ToString());       // Project to string value