C#多文本框过滤DataGridView时RowFilter报Mod运算符语法错误

Let's break down exactly why you're hitting this error and how to fix it cleanly:

The Root Cause #

Your section number filter line has two critical issues:

sb.Append("section_number like %" + Int32.Parse(section.Text) + "%");

1. Missing quotes around wildcards: In DataView's RowFilter syntax (which uses VB-style expressions), % without single quotes gets interpreted as the Mod (modulo) operator instead of a wildcard. This is why you're seeing the "Missing operand before 'Mod' operator" error.
2. Incorrect LIKE usage on numeric fields: section_number is a numeric type, but LIKE is designed for string comparisons. Directly using it on a number will cause parsing issues.

Fixed Code #

Here's a revised version that fixes these issues, adds error handling, and reduces injection risks:

StringBuilder sb = new StringBuilder();

// Handle document name search
if (!string.IsNullOrEmpty(documentName.Text))
{
    // Escape single quotes to avoid syntax errors (e.g., names like O'Neil)
    string safeDocumentName = documentName.Text.Replace("'", "''");
    sb.Append($"document_name LIKE '%{safeDocumentName}%'");
}

// Handle section number search
if (!string.IsNullOrEmpty(section.Text))
{
    // Add AND if we already have a filter
    if (sb.Length > 0)
    {
        sb.Append(" AND ");
    }
    
    // Validate input is a valid integer first
    if (int.TryParse(section.Text, out int sectionNumber))
    {
        // Convert numeric field to string for LIKE comparison
        sb.Append($"CONVERT(section_number, System.String) LIKE '%{sectionNumber}%'");
    }
    else
    {
        // Handle invalid input (adjust this to fit your UI flow)
        MessageBox.Show("Please enter a valid numeric section number.");
        return;
    }
}

// Apply the filter safely
DataTable dataTable = data.DataSource as DataTable;
if (dataTable != null)
{
    dataTable.DefaultView.RowFilter = sb.Length > 0 ? sb.ToString() : string.Empty;
}

Key Improvements #

• Properly quoted wildcards: The % wildcards are now wrapped in single quotes, so they're interpreted correctly by the RowFilter parser.
• Numeric field handling: We use CONVERT to turn the numeric section_number into a string before using LIKE—this is required for partial matching on numeric fields in DataView.
• Safer input handling:
  • string.IsNullOrEmpty is more readable and reliable than checking Length > 0.
  • int.TryParse prevents crashes if the user enters non-numeric text in the section field.
  • Escaping single quotes in the document name avoids syntax errors from names containing apostrophes.
• Cleaner conditional logic: The filter building is more structured and easier to maintain.

Bonus Tip #

If you only need exact matches for the section number (not partial matches), replace the LIKE line with a direct numeric comparison—it's faster and simpler:

sb.Append($"section_number = {sectionNumber}");

内容的提问来源于stack exchange，提问作者HowdyCowboy