FileAdapter.SeekRange Method

Estimated reading time: 4 minutes

Definition

Namespace: ASNA.DataGate.Client
Assembly: ASNA.QSys.DataGate.Client.dll

Positions the file pointer at the first record in the specified range in the file that the FileAdapter is working with.

void SeekRange([RangeMode mode, AdgKeyTable firstKey, RangeFirst rangeFirst, AdgKeyTable lastKey, RangeLast rangeLast)

Parameters

Type Parameter name Description
RangeMode mode The SeekMode to use when seeking the record.
AdgKeyTable firstKey The AdgKeyTable containing the key of the first record in the range to seek.
RangeFirst rangeFirst The RangeFirst value indicating whether to include the first record in the seek.
AdgKeyTable lastKey The AdgKeyTable containing the key of the last record in the range to seek.
RangeLast rangeLast The RangeLast value indicating whether to include the last record in the seek.

Example

    AdgConnection db = createAdgConnection("MyDatabaseName");
    FileAdapter dbFile = new FileAdapter(db, "*Libl/CSMASTERL1", "CSMASTERL1");
    dbFile.AccessMode = AccessMode.Read;
    AdgDataSet myDS = null;
    dbFile.OpenNewAdgDataSet(out myDS);

    /* The code below will find all of the sales for all customers with a number from 300 to 1400, 
    * and read all the customer numbers from lowest to highest. */
    AdgKeyTable key1 = myDS.NewKeyTable("RCSMASTL1");
    key1.Row["CSCUSTNO"] = Convert.ToDecimal(300);
    key1.KeyPartCount = 1;
    AdgKeyTable key2 = myDS.NewKeyTable("RCSMASTL1");
    key2.Row["CSCUSTNO"] = Convert.ToDecimal(1400);
    key2.KeyPartCount = 1;
    dbFile.SeekRange(RangeMode.First, key1, RangeFirst.Include, key2, RangeLast.Include);

    /* Read until we go past record 1400. */
    bool EOF = false;
    decimal Total = 0;
    while(!EOF)
    {
        try
        {
            dbFile.ReadSequential(myDS, ReadSequentialMode.Next, LockRequest.NoWait);
            for (int j=1; j <= 12; j++)
            {
                string number = j.ToString();
                if (number.Length < 2)
                    number = "0" + number;
                Total += Convert.ToDecimal(myDS.ActiveRow["CSSALES" + number]); 
            }
        }
        catch(dgException dgEx)
        {
            if (dgEx.Error == dgErrorNumber.dgEaEOF)
                EOF = true;
            else
                throw dgEx; //Throw exception if we didn't expect it.
        }
    }
    Console.WriteLine ($"Total sales for customers 300 to 1400 totaled {Total}"); 
    dbFile.Close();
    db.Close();

Remarks

The ReadRangeand SeekRange methods initiate a “range mode” for accessing records from an open file. Under this mode, subsequent FileAdapter sequential read methods (ReadSequentialand ReadSequentialEqual) restrict access to only records with keys that fall in the range specified by the key parameters. This mode allows programs to more efficiently access a certain set of records, especially when combined with the network record blocking feature (see FileOpenAttr.BlockingFactor).

The firstKey and lastKey parameters specify the range, along with the rangeFirst and rangeLast mode parameters. If the lastKey value specifies a key value which sorts prior to the firstKey value, the range specifies an empty set of records. Special values for the rangeFirst and rangeLast parameters allow the range to be extended to the beginning of the file (RangeFirst.Top) and the end of the file (RangeLast.Bottom). When one of these values is specified, the corresponding key value parameter is ignored.

SeekRange positions the file cursor on the first or last record in the range, as specified by the mode parameter (RangeMode.First or RangeMode.Last, respectively). If the range specifies an empty set of records, this method throws dgException with the Error property set to dgEaNOTFND.

Note that if FileAdapter was already in range mode, this method will cancel it and initiate a new range mode as specified.

See Also