| VSView Reporting Edition Reference > DataSource Object > DataSource Properties > FieldInfo Property |
Returns a variant array containing all field names, types, and size for the current report data source.
dataSource.FieldInfo[ = value As Variant ]
This property is useful in designer-type applications that need to retrieve information about the fields available in the source recordset.
The difference between retrieving this information directly from the recordset or from the FieldInfo property is that the source recordset is open only while the report is rendering, while the FieldInfo is available at all times.
The array returned contains one row for each field. Each row contains three columns, with the field name, ADO data type, and size (in bytes).
The example below shows a simple use for the FieldInfo property:
Dim v, i%
v = vsr.DataSource.FieldInfo
Debug.Print "** Fields in '"; vsr.ReportName; "'"
Debug.Print "Field#", "Name", "Type", "Size"
For i = 0 To UBound(v, 1)
Debug.Print "Field "; i,
Debug.Print v(i, 0), v(i, 1), v(i, 2)
Next
** Fields in 'Alphabetical List of Products'
Field# Name Type Size
Field 0 ProductID 3 4
Field 1 ProductName 202 40
Field 2 SupplierID 3 4
Field 3 CategoryID 3 4
Field 4 QuantityPerUnit 202 20
Field 5 UnitPrice 6 8
Field 6 UnitsInStock 2 2
Field 7 UnitsOnOrder 2 2
Field 8 ReorderLevel 2 2
Field 9 Discontinued 11 2
Field 10 CategoryName 202 15
The Report Designer uses this property extensively, to build field-pick lists and to automatically size report fields created by the New Report Wizard.
To use the FieldInfo property in Visual C++ programs, you need to use the system APIs designed to manipulate SAFEARRAY structures. The example below shows how that works:
// import interfaces for VSReports7 control
#import "VSRpt8.ocx" no_namespace
// use FieldInfo to get field information for a given report
BOOL ListFields(IVSReportPtr spReport)
{
USES_CONVERSION;
// get data source
if (spReport == NULL) return FALSE;
IDataSourcePtr spDS = spReport->DataSource;
if (spDS == NULL) return FALSE;
// get FieldInfo array
CComVariant v = spDS->FieldInfo;
if (V_VT(&v) != (VT_ARRAY | VT_VARIANT)) return FALSE;
ATLASSERT(v.parray->cDims == 2);
// scan FieldInfo array and display the information
long pIndex[2];
for (long i = 0;; i++) {
// reading array row I
pIndex[0] = i;
// get field name
pIndex[1] = 0;
CComVariant vName;
CComBSTR strName;
if (FAILED(SafeArrayGetElement(v.parray, pIndex, &vName))) break;
if (vName.vt == VT_BSTR) strName = V_BSTR(&vName);
// get field type
pIndex[1] = 1;
CComVariant vType;
if (FAILED(SafeArrayGetElement(v.parray, pIndex, &vType))) break;
// get field size
pIndex[1] = 2;
CComVariant vSize;
if (FAILED(SafeArrayGetElement(v.parray, pIndex, &vSize))) break;
// show the information
ATLTRACE("Field %d %s %d %d\n",
i, W2T(strName), V_I4(&vType), V_I4(&vSize));
}
// done
return TRUE;
}
The #import statement is very important. It loads all interfaces and constants defined by the control. The CComVariant, CComBSTR, USES_CONVERSION, and ATLTRACE symbols are defined by ATL. Other class libraries have similar constructs and classes (for example, MFC had COleVariant, CString, and TRACE).
Variant