IExpressionEval::LoadExpr
.gif "Ee824499.c++_off(en-US,CS.10).gif")
.gif "Ee824499.vb_on(en-US,CS.10).gif")
Use this method to pre-compile an expression, and if successful, load the expression into the expression cache.
Definition
HRESULT IExpressionEval::LoadExpr(longnExprID);
Parameters
nExprID
[in] A positive long that contains the identifier of the expression to load into the expression cache.
Return Values
This method returns an HRESULT indicating whether it completed successfully. See the Error Values section for more details.
Error Values
This method returns S_OK (0x00000000) to indicate success and either standard or custom COM HRESULT error values to indicate failure. For more information about standard COM errors, see Standard COM Errors.
The following table shows the custom COM errors that this method can return.
| Constant | Value | Description |
| E_EXPR_BADARGTYPE | 0x81100018 | Argument datatype info missing from expression, or unrecognized argument data type encountered in expression |
| E_EXPR_BADARGVALUE | 0x81100022 | Invalid expression argument value, or impossible conversion |
| E_EXPR_BADCLAUSE | 0x81100016 | Invalid clause encountered |
| E_EXPR_BADCONNECTION | 0x8110001F | Invalid connection |
| E_EXPR_BADEXPRID | 0x8110000A | Invalid expression ID specified |
| E_EXPR_BADOPER | 0x81100017 | Operator missing, unrecognized operator encountered, or type mismatch |
| E_EXPR_BADTERM | 0x81100015 | Term type missing, or unrecognized term type encountered |
| E_EXPR_BADXML | 0x81100014 | An unrecognized XML element was encountered |
| E_EXPR_NOCONNECTIONSTRING | 0x8110000D | No connection string specified |
| E_EXPR_NOTFOUND | 0x81100012 | Could not find the specified expression ID, nExprID, in the expression store |
| E_EXPR_XMLPARSE | 0x81100013 | XML DOM object parsing error |
Additional information may be available using the global Err object, which can be accessed using the API function GetErrorInfo. In particular, the GetDescription method of the IErrorInfo interface may return a text description of the error.
Remarks
If the specified expression is already loaded in the expression cache at the time of the call, it will be reloaded.
The LoadExpr method increments the read-only ExprCount property by one when it loads an expression into the expression cache.
With the exception of XML fragments, only expressions that exist in the expression cache may be evaluated. The Eval method loads an expression from the expression store that is not preloaded into the expression cache.
Use the LoadAll method to load all expressions into the expression cache. Use the FlushExpr method to remove an expression from the expression cache.
The Connect method must be called before using the LoadExpr method.