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namespace System.Web.UI.WebControls.Expressions {
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
internal static class ExpressionHelper {
public static Expression GetValue(Expression exp) {
Type realType = GetUnderlyingType(exp.Type);
if (realType == exp.Type) {
return exp;
}
return Expression.Convert(exp, realType);
}
public static Type GetUnderlyingType(Type type) {
// Get the type from Nullable types
if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>)) {
return type.GetGenericArguments()[0];
}
return type;
}
public static object BuildObjectValue(object value, Type type) {
return System.Web.UI.WebControls.DataSourceHelper.BuildObjectValue(value, type, String.Empty);
}
public static Expression CreatePropertyExpression(Expression parameterExpression, string propertyName) {
if (parameterExpression == null) {
return null;
}
if (String.IsNullOrEmpty(propertyName)) {
return null;
}
Expression propExpression = null;
string[] props = propertyName.Split('.');
foreach (var p in props) {
if (propExpression == null) {
propExpression = Expression.PropertyOrField(parameterExpression, p);
}
else {
propExpression = Expression.PropertyOrField(propExpression, p);
}
}
return propExpression;
}
public static IQueryable Where(this IQueryable source, LambdaExpression lambda) {
return Call(source, "Where", lambda, source.ElementType);
}
public static IQueryable Call(this IQueryable source, string queryMethod, Type[] genericArgs, params Expression[] arguments) {
if (source == null) {
throw new ArgumentNullException("source");
}
return source.Provider.CreateQuery(
Expression.Call(
typeof(Queryable), queryMethod,
genericArgs,
arguments));
}
public static IQueryable Call(this IQueryable source, string queryableMethod, LambdaExpression lambda, params Type[] genericArgs) {
if (source == null) {
throw new ArgumentNullException("source");
}
return source.Provider.CreateQuery(
Expression.Call(
typeof(Queryable), queryableMethod,
genericArgs,
source.Expression, Expression.Quote(lambda)));
}
public static Expression Or(IEnumerable<Expression> expressions) {
Expression orExpression = null;
foreach (Expression e in expressions) {
if (e == null) {
continue;
}
if (orExpression == null) {
orExpression = e;
}
else {
orExpression = Expression.OrElse(orExpression, e);
}
}
return orExpression;
}
public static Expression And(IEnumerable<Expression> expressions) {
Expression andExpression = null;
foreach (Expression e in expressions) {
if (e == null) {
continue;
}
if (andExpression == null) {
andExpression = e;
}
else {
andExpression = Expression.AndAlso(andExpression, e);
}
}
return andExpression;
}
}
}
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