Check if CString contains specific Text MFC

Checking for Substring Existence in MFC CString Objects

Learn various methods to efficiently determine if a CString object contains a specific substring in MFC applications, covering both case-sensitive and case-insensitive searches.

In MFC (Microsoft Foundation Classes) development, working with CString objects is a common task. One frequent requirement is to check if a CString contains a particular piece of text or a substring. This article explores several robust methods to achieve this, catering to different needs such as case sensitivity and performance considerations. Understanding these techniques is crucial for effective string manipulation in MFC applications.

Using CString::Find() for Basic Substring Checks

The CString::Find() method is the most straightforward way to check for the presence of a substring. It returns the zero-based index of the first occurrence of the substring within the CString object. If the substring is not found, it returns -1. This method performs a case-sensitive search by default.

CString strMain = _T("Hello, World!");
CString strSearch = _T("World");

if (strMain.Find(strSearch) != -1)
{
    // Substring 'World' was found
    AfxMessageBox(_T("Found 'World'!"));
}
else
{
    // Substring not found
    AfxMessageBox(_T("Did not find 'World'."));
}

// Example with a substring not present
CString strNotFound = _T("MFC");
if (strMain.Find(strNotFound) == -1)
{
    AfxMessageBox(_T("Did not find 'MFC'."));
}

Basic usage of CString::Find() for case-sensitive substring detection.

Performing Case-Insensitive Searches

When case sensitivity is not desired, CString::Find() alone is insufficient. You need to convert both the main string and the substring to a common case (either uppercase or lowercase) before performing the search. This ensures that 'world' matches 'World', 'WORLD', or 'WoRlD'.

CString strMain = _T("Hello, World!");
CString strSearch = _T("world");

// Convert both strings to lowercase for case-insensitive comparison
if (strMain.MakeLower().Find(strSearch.MakeLower()) != -1)
{
    // Substring 'world' (case-insensitive) was found
    AfxMessageBox(_T("Found 'world' (case-insensitive)!"));
}

// Alternatively, use MakeUpper()
CString strMainUpper = strMain;
CString strSearchUpper = strSearch;
if (strMainUpper.MakeUpper().Find(strSearchUpper.MakeUpper()) != -1)
{
    AfxMessageBox(_T("Found 'world' (case-insensitive, using upper)!"));
}

Case-insensitive search using MakeLower() or MakeUpper() before Find().

flowchart TD
    A[Start] --> B{Need Case-Sensitive?}
    B -- Yes --> C[Use CString::Find()]
    B -- No --> D[Convert Both to Lower/Upper Case]
    D --> E[Use CString::Find() on Converted Strings]
    C --> F{Result != -1?}
    E --> F
    F -- Yes --> G[Substring Found]
    F -- No --> H[Substring Not Found]
    G --> I[End]
    H --> I

Decision flow for checking CString content.

Advanced Search with CString::FindOneOf()

While Find() searches for a specific substring, FindOneOf() searches for the first occurrence of any character from a specified set of characters. This can be useful in scenarios where you need to detect the presence of any delimiter or special character. It also returns the index of the first match or -1 if no characters from the set are found.

CString strText = _T("This is a test string with, punctuation.");
CString strDelimiters = _T(",.;!?");

if (strText.FindOneOf(strDelimiters) != -1)
{
    AfxMessageBox(_T("String contains at least one delimiter."));
}
else
{
    AfxMessageBox(_T("String does not contain any specified delimiters."));
}

CString strNoDelimiters = _T("CleanString");
if (strNoDelimiters.FindOneOf(strDelimiters) == -1)
{
    AfxMessageBox(_T("CleanString has no delimiters."));
}

Using CString::FindOneOf() to check for any character from a set.