Merge pull request #117 from netcorepal/whereif

add whereif

src/NetCorePal.Extensions.Dto/IQueryableExtensions.cs

@@ -0,0 +1,30 @@
+using System.Linq.Expressions;
+
+namespace NetCorePal.Extensions.Dto;
+
+/// <summary>
+/// 
+/// </summary>
+public static class IQueryableExtensions
+{
+    /// <summary>
+    /// 根据条件决定是否使用表达式进行where查询
+    /// </summary>
+    /// <param name="source">原始查询集合</param>
+    /// <param name="condition">如果为true，则使用where表达式，否则不使用表达式</param>
+    /// <param name="predicate">用于where的条件表达式</param>
+    /// <typeparam name="T">The type of the data in the data source</typeparam>
+    /// <returns>如果condition为true，则返回使用了表达式predicate的where结果；否则，返回原source</returns>
+    public static IQueryable<T> WhereIf<T>(
+        this IQueryable<T> source,
+        bool condition,
+        Expression<Func<T, bool>> predicate)
+    {
+        if (condition)
+        {
+            return source.Where(predicate);
+        }
+
+        return source;
+    }
+}

test/NetCorePal.Extensions.Dto.Tests/IQueryableExtensionsTests.cs

@@ -0,0 +1,17 @@
+namespace NetCorePal.Extensions.Dto.Tests;
+
+public class IQueryableExtensionsTests
+{
+    [Fact]
+    public void WhereIfTests()
+    {
+        var data = new List<int> { 1, 2, 3, 4, 5 }.AsQueryable();
+        var result = data.WhereIf(true, x => x > 3).ToList();
+        Assert.Equal(2, result.Count);
+        Assert.Equal(4, result[0]);
+        Assert.Equal(5, result[1]);
+
+        result = data.WhereIf(false, x => x > 3).ToList();
+        Assert.Equal(5, result.Count);
+    }
+}