EntityFrameworkCore: PostgreSQL Useful Extensions

Entity Framework Core extensions for PostgreSQL: case-insensitive string matching (ILike, EqualsLowerCase), dynamic OR query composition (OrWhere), conditional filtering (WhereIf), and seamless LINQ-to-SQL translation for efficient, expressive queries.

Features

• EqualsLowerCase: Case-insensitive equality using lower() on both sides: string.EqualsLowerCase(value).
• ILike: Case-insensitive pattern matching translated to PostgreSQL ILIKE with proper escaping. Methods: string.ILike(pattern), string.ILikeStartsWith(value), string.ILikeEndsWith(value), string.ILikeContains(value).
• OrWhere: Combines a new predicate with the previous Where predicate using OR, enabling alternative conditions in a single Where chain.
• WhereIf: Adds filters conditionally (e.g., only when a value is non-empty or a flag is true) to keep queries clean and composable.

Requirements

• .NET 10.0
• Entity Framework Core 10.x
• Npgsql.EntityFrameworkCore.PostgreSQL 10.x

Note: For .NET 8 and .NET 9 support, use package versions v8.x and v9.x respectively.

Installation

Using .NET CLI:

dotnet add package Techbrifut.EntityFrameworkCore.PostgreSQL.UsefulExtensions

Or via NuGet Package Manager: search for Techbrifut.EntityFrameworkCore.PostgreSQL.UsefulExtensions.

Quick start

Register the translators once when configuring your DbContext options:

using Techbrifut.EntityFrameworkCore.PostgreSQL.UsefulExtensions; var optionsBuilder = new DbContextOptionsBuilder() .UseNpgsql("Your connection string") .UseUsefulExtensions(); // << enable extensions

For applications using .NET's built-in DI container (e.g., ASP.NET Core, Blazor, or hosted services), configure your DbContext in the service collection:

using Techbrifut.EntityFrameworkCore.PostgreSQL.UsefulExtensions; services.AddDbContext<AppDbContext>(options => options .UseNpgsql("Your connection string") .UseUsefulExtensions() // << enable extensions );

EqualsLowerCase

Case-insensitive equality without patterns. This translates your LINQ into lower(..) = lower(..) in SQL, so both sides are converted to lowercase before comparing.

var users = await db.Users.AsNoTracking() .Where(user => user.FirstName.EqualsLowerCase("alice")) .ToListAsync();

Generated SQL (conceptually)

WHERE lower(u."Name") = lower(@__name)

• Consider proper indexing (e.g., functional indexes on lower(column)) when using case-insensitive comparisons for performance.
• Prefer EqualsLowerCase when you need exact equality ignoring case. Use ILike* helpers for pattern-based matching (contains/starts/ends).

ILike

Case-insensitive pattern matching using PostgreSQL's ILIKE operator. The extension automatically handles proper escaping of special characters (%, _, \) to prevent unintended pattern matching.

ILike

Use custom patterns with % and _ wildcards:

var users = await db.Users.AsNoTracking() .Where(user => user.FullName.ILike("%john%")) .ToListAsync();

Generated SQL (conceptually)

WHERE u."FullName" ILIKE '%john%' ESCAPE '\'

ILikeStartsWith

Match strings that start with a value:

var users = await db.Users.AsNoTracking() .Where(user => user.LastName.ILikeStartsWith("thomp")) .ToListAsync();

Generated SQL (conceptually)

WHERE u."LastName" ILIKE REPLACE(REPLACE(REPLACE(@__value, '\', '\\'), '%', '\%'), '_', '\_') || '%' ESCAPE '\'

ILikeEndsWith

Match strings that end with a value:

var users = await db.Users.AsNoTracking() .Where(user => user.LastName.ILikeEndsWith("son")) .ToListAsync();

Generated SQL (conceptually)

WHERE u."LastName" ILIKE '%' || REPLACE(REPLACE(REPLACE(@__value, '\', '\\'), '%', '\%'), '_', '\_') ESCAPE '\'

ILikeContains

Match strings that contain a value:

var users = await db.Users.AsNoTracking() .Where(user => user.LastName.ILikeContains("il")) .ToListAsync(); WHERE u."LastName" ILIKE '%' || REPLACE(REPLACE(REPLACE(@__value, '\', '\\'), '%', '\%'), '_', '\_') || '%' ESCAPE '\'

• The ILike* helpers (ILikeStartsWith, ILikeEndsWith, ILikeContains) automatically escape special LIKE characters in the input value to ensure literal matching.
• Use the basic ILike method when you need full control over pattern matching with explicit wildcards.
• Consider GIN/GiST indexes with pg_trgm extension for better performance on pattern matching queries.

OrWhere

Combines a new predicate with the previous Where predicate using OR logic, enabling alternative conditions in a single query chain. This is particularly useful when you need to apply conditional OR logic dynamically.

Basic Usage

Chain OrWhere after a Where call to create an OR condition:

var users = await db.Users.AsNoTracking() .Where(user => user.FirstName.EqualsLowerCase("Alice")) .OrWhere(user => user.LastName.EqualsLowerCase("Smith")) .ToListAsync();

Generated SQL (conceptually)

WHERE lower(u."FirstName") = lower('Alice') OR lower(u."LastName") = lower('Smith')

Grouping Filters with BeginWhereGroup and EndWhereGroup

When building dynamic queries with conditional filters, you often need to group multiple conditions together and combine them with other filters using OR logic. The BeginWhereGroup() and EndWhereGroup() methods allow you to create parenthesized groups of AND conditions that can be combined with OR logic.

Basic Grouping

Use BeginWhereGroup() to start a group and EndWhereGroup() to close it. All Where or WhereIf calls between these methods are combined with AND and wrapped in parentheses:

var filter = new Filter(FirstName: "Quinn", LastName: "White"); var users = await db.Users.AsNoTracking() .BeginWhereGroup() .WhereIfIsNotNullOrEmpty(filter.FirstName, user => user.FirstName.EqualsLowerCase(filter.FirstName!)) .WhereIfIsNotNullOrEmpty(filter.LastName, user => user.LastName.EqualsLowerCase(filter.LastName!)) .EndWhereGroup() .ToListAsync();

Generated SQL (conceptually)

WHERE (lower(u."FirstName") = lower('Quinn') AND lower(u."LastName") = lower('White'))

Combining Groups with OR Logic

The real power of grouping comes when combining groups with OrWhere or OrWhereIf:

var filter = new Filter(FirstName: "Quinn", LastName: "White"); var specialFilter = new { IncludeAlice = true }; var users = await db.Users.AsNoTracking() .BeginWhereGroup() .WhereIfIsNotNullOrEmpty(filter.FirstName, user => user.FirstName.EqualsLowerCase(filter.FirstName!)) .WhereIfIsNotNullOrEmpty(filter.LastName, user => user.LastName.EqualsLowerCase(filter.LastName!)) .EndWhereGroup() .OrWhereIf(specialFilter.IncludeAlice, user => user.FirstName.EqualsLowerCase("Alice")) .ToListAsync();

Generated SQL (conceptually)

WHERE (lower(u."FirstName") = lower('Quinn') AND lower(u."LastName") = lower('White')) OR lower(u."FirstName") = lower('Alice')

This creates a query that returns users matching both first and last name from the filter, OR users named Alice.

Conditional Grouping

Use BeginWhereGroupIf() and EndWhereGroupIf() to conditionally apply grouping based on a condition:

bool applyComplexFilter = true; var filter = new Filter(FirstName: "Quinn", LastName: "White"); var users = await db.Users.AsNoTracking() .BeginWhereGroupIf(applyComplexFilter) .WhereIfIsNotNullOrEmpty(filter.FirstName, user => user.FirstName.EqualsLowerCase(filter.FirstName!)) .WhereIfIsNotNullOrEmpty(filter.LastName, user => user.LastName.EqualsLowerCase(filter.LastName!)) .EndWhereGroupIf(applyComplexFilter) .ToListAsync();

If applyComplexFilter is false, the conditions are applied without grouping parentheses.

• Always pair BeginWhereGroup() with EndWhereGroup(). Calling EndWhereGroup() without a matching BeginWhereGroup() will throw an InvalidOperationException.
• Groups are particularly useful when building complex dynamic queries with multiple optional filter sets that need to be OR-ed together.
• Empty groups (where all conditional filters are skipped) are automatically removed from the query.
• Use BeginWhereGroupIf() and EndWhereGroupIf() with the same condition value to ensure proper pairing.

And() with OrWhere groups

Use And() to join OrWhere groups with the logical AND operator. It closes the current OR group and starts a new one that will be AND-ed with the previous group. The regular Where() cannot be used after And().

var users = await db.Users.AsNoTracking() .OrWhere(user => user.FirstName.EqualsLowerCase("Alice")) .OrWhere(user => user.FirstName.EqualsLowerCase("Bob")) .And() .OrWhere(user => user.LastName.EqualsLowerCase("Smith")) .OrWhere(user => user.LastName.EqualsLowerCase("Taylor")) .ToListAsync();

Generated SQL (conceptually)

WHERE (lower(u."FirstName") = lower('Alice') OR lower(u."FirstName") = lower('Bob')) AND (lower(u."LastName") = lower('Smith') OR lower(u."LastName") = lower('Taylor'))

• Use And() only between OrWhere chains to start a new OR-group.
• Do not call Where() immediately after And(); continue with OrWhere to build the next group.
• AndIf(condition) conditionally applies And(); if condition is false, the chain continues without introducing a new AND group.

WhereIf

Conditionally applies filters to queries only when specified conditions are met, keeping your query logic clean and composable. This eliminates the need for branching logic when building dynamic queries based on optional filter parameters.

WhereIf

Apply a filter only when a condition is true:

bool includeActive = true; var users = await db.Users.AsNoTracking() .WhereIf(includeActive, user => user.IsActive) .ToListAsync();

Generated SQL (conceptually)

WHERE u."IsActive" = TRUE

If includeActive is false, no filter is applied and the query returns all users.

WhereIfIsNotNullOrEmpty (String)

Apply a filter only when a string value is not null or empty:

var filter = new Filter(FirstName: "George", LastName: null); var users = await db.Users.AsNoTracking() .WhereIfIsNotNullOrEmpty(filter.FirstName, user => user.FirstName.EqualsLowerCase(filter.FirstName!)) .WhereIfIsNotNullOrEmpty(filter.LastName, user => user.LastName.EqualsLowerCase(filter.LastName!)) .ToListAsync();

Generated SQL (conceptually)

WHERE lower(u."FirstName") = lower('George')

The LastName filter is not applied because the value is null.

WhereIfIsNotNullOrWhiteSpace

Apply a filter only when a string value is not null, empty, or whitespace:

string name = " "; // whitespace only var users = await db.Users.AsNoTracking() .WhereIfIsNotNullOrWhiteSpace(name, user => user.FullName.ILikeContains(name)) .ToListAsync();

No filter is applied since the value contains only whitespace, returning all users.

WhereIfIsNotNullOrEmpty (Guid)

Apply a filter only when a Guid value is not null or empty:

Guid? departmentId = Guid.NewGuid(); var users = await db.Users.AsNoTracking() .WhereIfIsNotNullOrEmpty(departmentId, user => user.DepartmentId == departmentId) .ToListAsync();

Generated SQL (conceptually)

WHERE u."DepartmentId" = @__departmentId

OrWhereIf Variants

Combine conditional filters with OR logic. These methods follow the same patterns as their WhereIf counterparts but use OR instead of AND:

• OrWhereIf: Apply an OR filter when a condition is true
• OrWhereIfIsNotNullOrEmpty: Apply an OR filter when a string is not null or empty
• OrWhereIfIsNotNullOrWhiteSpace: Apply an OR filter when a string is not null, empty, or whitespace
• OrWhereIfIsNotNullOrEmpty (Guid): Apply an OR filter when a Guid is not null or empty

var filter = new Filter(FirstName: string.Empty, LastName: "White"); var specialFilter = new { IncludeAlice = true }; var users = await db.Users.AsNoTracking() .WhereIfIsNotNullOrEmpty(filter.FirstName, user => user.FirstName.EqualsLowerCase(filter.FirstName!)) .WhereIfIsNotNullOrEmpty(filter.LastName, user => user.LastName.EqualsLowerCase(filter.LastName!)) .OrWhereIf(specialFilter.IncludeAlice, user => user.FirstName.EqualsLowerCase("Alice")) .ToListAsync();

Generated SQL (conceptually)

WHERE lower(u."LastName") = lower('White') OR lower(u."FirstName") = lower('Alice')