Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Modified version. This class is probably better than many other ones you can find around :-) This is because this version support direct properties (<code>p =&gt; p.B</code>) (as everyone else :-) ), nested properties (<code>p =&gt; p.B.C.D</code>), fields (both "terminal" and "in the middle", so in <code>p =&gt; p.B.C.D</code> both <code>B</code> and <code>D</code> could be fields) and "inner" casting of types (so <code>p =&gt; ((BType)p.B).C.D</code> and <code>p =&gt; (p.B as BType).C.D)</code>. The only thing that isn't supported is casting of the "terminal" element (so no <code>p =&gt; (object)p.B</code>). </p> <p>There are two "codepaths" in the generator: for simple Expressions (<code>p =&gt; p.B</code>) and for "nested" expressions. There are code variants for .NET 4.0 (that has the <code>Expression.Assign</code> expression type). From some benchmarks of mine the fastest delegates are: "simple" <code>Delegate.CreateDelegate</code> for properties, <code>Expression.Assign</code> for fields and "simple" <code>FieldSetter</code> for fields (this one is just a little slower than <code>Expression.Assign</code> for fields). So under .NET 4.0 you should take away all the code marked as 3.5.</p> <p>Part of the code isn't mine. The initial (simple) version was based on the Fluent NHibernate code (but it supported only direct properties), some other parts are based on code from <a href="https://stackoverflow.com/questions/321650/how-do-i-set-a-field-value-in-an-c-expression-tree/321686#321686">How do I set a field value in an C# Expression tree?</a> and <a href="https://stackoverflow.com/questions/208969/assignment-in-net-3-5-expression-trees/3972359#3972359">Assignment in .NET 3.5 expression trees</a>.</p> <pre><code>public static class FluentTools { public static Action&lt;T, TValue&gt; GetterToSetter&lt;T, TValue&gt;(Expression&lt;Func&lt;T, TValue&gt;&gt; getter) { ParameterExpression parameter; Expression instance; MemberExpression propertyOrField; GetMemberExpression(getter, out parameter, out instance, out propertyOrField); // Very simple case: p =&gt; p.Property or p =&gt; p.Field if (parameter == instance) { if (propertyOrField.Member.MemberType == MemberTypes.Property) { // This is FASTER than Expression trees! (5x on my benchmarks) but works only on properties PropertyInfo property = propertyOrField.Member as PropertyInfo; MethodInfo setter = property.GetSetMethod(); var action = (Action&lt;T, TValue&gt;)Delegate.CreateDelegate(typeof(Action&lt;T, TValue&gt;), setter); return action; } #region .NET 3.5 else // if (propertyOrField.Member.MemberType == MemberTypes.Field) { // 1.2x slower than 4.0 method, 5x faster than 3.5 method FieldInfo field = propertyOrField.Member as FieldInfo; var action = FieldSetter&lt;T, TValue&gt;(field); return action; } #endregion } ParameterExpression value = Expression.Parameter(typeof(TValue), "val"); Expression expr = null; #region .NET 3.5 if (propertyOrField.Member.MemberType == MemberTypes.Property) { PropertyInfo property = propertyOrField.Member as PropertyInfo; MethodInfo setter = property.GetSetMethod(); expr = Expression.Call(instance, setter, value); } else // if (propertyOrField.Member.MemberType == MemberTypes.Field) { expr = FieldSetter(propertyOrField, value); } #endregion //#region .NET 4.0 //// For field access it's 5x faster than the 3.5 method and 1.2x than "simple" method. For property access nearly same speed (1.1x faster). //expr = Expression.Assign(propertyOrField, value); //#endregion return Expression.Lambda&lt;Action&lt;T, TValue&gt;&gt;(expr, parameter, value).Compile(); } private static void GetMemberExpression&lt;T, U&gt;(Expression&lt;Func&lt;T, U&gt;&gt; expression, out ParameterExpression parameter, out Expression instance, out MemberExpression propertyOrField) { Expression current = expression.Body; while (current.NodeType == ExpressionType.Convert || current.NodeType == ExpressionType.TypeAs) { current = (current as UnaryExpression).Operand; } if (current.NodeType != ExpressionType.MemberAccess) { throw new ArgumentException(); } propertyOrField = current as MemberExpression; current = propertyOrField.Expression; instance = current; while (current.NodeType != ExpressionType.Parameter) { if (current.NodeType == ExpressionType.Convert || current.NodeType == ExpressionType.TypeAs) { current = (current as UnaryExpression).Operand; } else if (current.NodeType == ExpressionType.MemberAccess) { current = (current as MemberExpression).Expression; } else { throw new ArgumentException(); } } parameter = current as ParameterExpression; } #region .NET 3.5 // Based on https://stackoverflow.com/questions/321650/how-do-i-set-a-field-value-in-an-c-expression-tree/321686#321686 private static Action&lt;T, TValue&gt; FieldSetter&lt;T, TValue&gt;(FieldInfo field) { DynamicMethod m = new DynamicMethod("setter", typeof(void), new Type[] { typeof(T), typeof(TValue) }, typeof(FluentTools)); ILGenerator cg = m.GetILGenerator(); // arg0.&lt;field&gt; = arg1 cg.Emit(OpCodes.Ldarg_0); cg.Emit(OpCodes.Ldarg_1); cg.Emit(OpCodes.Stfld, field); cg.Emit(OpCodes.Ret); return (Action&lt;T, TValue&gt;)m.CreateDelegate(typeof(Action&lt;T, TValue&gt;)); } // Based on https://stackoverflow.com/questions/208969/assignment-in-net-3-5-expression-trees/3972359#3972359 private static Expression FieldSetter(Expression left, Expression right) { return Expression.Call( null, typeof(FluentTools) .GetMethod("AssignTo", BindingFlags.NonPublic | BindingFlags.Static) .MakeGenericMethod(left.Type), left, right); } private static void AssignTo&lt;T&gt;(ref T left, T right) // note the 'ref', which is { // important when assigning left = right; // to value types! } #endregion } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POExpression<Func<TModel,string>> to Expression<Action<TModel>> "Getter" to "Setter"
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCommunity
    1. USxanatos
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POExpression<Func<TModel,string>> to Expression<Action<TModel>> "Getter" to "Setter"
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUndeletion
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COThis looks very promising, i'm getting an argumentexception on the CreateDelegate call tough, "Error binding to target method." the expression in debug mode has a NodeType of Parameter, and the member i'm trying to set is a DateTime
      singulars
      1. PO
      1. USMichiel Cornille
    2. CO@Mvision What are you trying to bind? This will work only on public Properties.
      singulars
      1. PO
      1. USxanatos
    3. COI assume all properties i'm binding are public, i handpick them from EF4 entities like this : customer=>customer.DateCreated etc
      singulars
      1. PO
      1. USMichiel Cornille
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload