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Implementation of parameterized sql queries using string interpolation handlers
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using System.Data.Common; | |
using System.Runtime.CompilerServices; | |
using System.Text; | |
using Npgsql; | |
GetCatalogItemsSql(null, null, null, 10); | |
void GetCatalogItemsSql(int? catalogBrandId, int? before, int? after, int pageSize) | |
{ | |
// This looks like it would be susceptible to SQL injection, but it's not. | |
// The interpolated string is converted to a FromSqlInterpolatedStringHandler which will turn those | |
// interpolated values in to parameterized values. | |
SqlQuery($""" | |
SELECT * | |
FROM "Catalog" AS c | |
WHERE ({catalogBrandId} IS NULL OR c."CatalogBrandId" = {catalogBrandId}) | |
AND ({before} IS NULL OR c."Id" < {before}) | |
AND ({after} IS NULL OR c."Id" >= {after}) | |
ORDER BY c."Id" | |
LIMIT {pageSize + 1} | |
"""); | |
} | |
void SqlQuery(in FromSqlInterpolatedStringHandler builder) | |
{ | |
Console.WriteLine(builder.GetQueryText()); | |
Console.WriteLine(); | |
foreach (var p in builder.GetParameters()) | |
{ | |
Console.WriteLine($"{p.ParameterName} = {(p.Value is null ? "NULL" : p.Value.ToString())}"); | |
} | |
} | |
[InterpolatedStringHandler] | |
public ref struct FromSqlInterpolatedStringHandler | |
{ | |
StringBuilder _builder; | |
int _paramterCount; | |
DbParameter[]? _parameters; | |
public FromSqlInterpolatedStringHandler(int literalLength, int formattedCount) | |
{ | |
_builder = new StringBuilder(literalLength); | |
_parameters = formattedCount > 0 ? new DbParameter[formattedCount] : null; | |
} | |
public void AppendLiteral(string s) | |
{ | |
_builder.Append(s); | |
} | |
public void AppendFormatted<T>(T t) | |
{ | |
var parameterName = $"@p{_paramterCount}"; | |
_builder.Append(parameterName); | |
_parameters![_paramterCount++] = new NpgsqlParameter<T>(parameterName, t); | |
} | |
internal string GetQueryText() => _builder.ToString(); | |
internal DbParameter[] GetParameters() => _parameters ?? Array.Empty<DbParameter>(); | |
} |
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Nice! Can I do something similiar in SQL Server? I Have a procedure that generate tables based on values stored in tables, and I believe they're exposed to sql injection risk :(