Entity framework EF动态查询类

在使用字符串函数“contains”成功地实现了一个like函数之后，我注意到通配符在转换为sql时被转义

当我搜索一条以p开头并有数字13的街道时。我用“%”替换所有空格，但EF将其转义。输出查询如下所示：

SELECT " FROM Customer WHERE (LOWER([Street]) LIKE N'%p~%13%' ESCAPE N'~')

public static Expression<Func<T, bool>> Create<T>(string propertyName, ComparisonOperators comparisonOperator, dynamic comparedValue1, dynamic comparedValue2 = null)
{
    ParameterExpression parameterExpression = Expression.Parameter(typeof(T), "x");
    MemberExpression memberExpression = Expression.MakeMemberAccess(parameterExpression, typeof(T).GetProperty(propertyName));
    ConstantExpression constantExpression = Expression.Constant(comparedValue1, comparedValue1.GetType());
    Expression expressionBody = null;

    switch (comparisonOperator)
    {
        ...

        case ComparisonOperators.Contains:
            expressionBody = Expression.Call(GetLowerCasePropertyAccess(memberExpression), ContainsMethod, Expression.Constant(comparedValue1.ToLower()));
            break;
    }

    return Expression.Lambda<Func<T, bool>>(expressionBody, new ParameterExpression[] { parameterExpression });
}

private static MethodCallExpression GetLowerCasePropertyAccess(MemberExpression propertyAccess)
{
    var stringExpression = GetConvertToStringExpression(propertyAccess);
    if (stringExpression == null)
        throw new Exception(string.Format("Not supported property type {0}", propertyAccess.Type));

    return Expression.Call(stringExpression, typeof(string).GetMethod("ToLower", Type.EmptyTypes));
}

private static Expression GetConvertToStringExpression(Expression e)
{
    // if property string - no cast needed
    // else - use SqlFunction.StringConvert(double?) or SqlFunction.StringConvert(decimal?);
    Expression strExpression = null;
    if (e.Type == typeof(string)) strExpression = e;
    else
    {
        var systemType = Nullable.GetUnderlyingType(e.Type) ?? e.Type;
        if (systemType == typeof(int) || systemType == typeof(long) || systemType == typeof(double) || systemType == typeof(short) || systemType == typeof(byte))
        {
            // cast int to double
            var doubleExpr = Expression.Convert(e, typeof(double?));
            strExpression = Expression.Call(StringConvertMethodDouble, doubleExpr);
        }
        else if (systemType == typeof(decimal))
        {
            // call decimal version of StringConvert method
            // cast to nullable decimal
            var decimalExpr = Expression.Convert(e, typeof(decimal?));
            strExpression = Expression.Call(StringConvertMethodDecimal, decimalExpr);
        }
    }
    return strExpression;
}

private static readonly MethodInfo ContainsMethod = typeof(String).GetMethod("Contains", new Type[] { typeof(String) });
private static readonly MethodInfo StringConvertMethodDouble = typeof(SqlFunctions).GetMethod("StringConvert", new Type[] { typeof(double?) });
private static readonly MethodInfo StringConvertMethodDecimal = typeof(SqlFunctions).GetMethod("StringConvert", new Type[] { typeof(decimal?) });

在其中一个博客中，有人建议改用patindex。我只是不知道如何实现这一点

我当前的代码如下所示：

SELECT " FROM Customer WHERE (LOWER([Street]) LIKE N'%p~%13%' ESCAPE N'~')

public static Expression<Func<T, bool>> Create<T>(string propertyName, ComparisonOperators comparisonOperator, dynamic comparedValue1, dynamic comparedValue2 = null)
{
    ParameterExpression parameterExpression = Expression.Parameter(typeof(T), "x");
    MemberExpression memberExpression = Expression.MakeMemberAccess(parameterExpression, typeof(T).GetProperty(propertyName));
    ConstantExpression constantExpression = Expression.Constant(comparedValue1, comparedValue1.GetType());
    Expression expressionBody = null;

    switch (comparisonOperator)
    {
        ...

        case ComparisonOperators.Contains:
            expressionBody = Expression.Call(GetLowerCasePropertyAccess(memberExpression), ContainsMethod, Expression.Constant(comparedValue1.ToLower()));
            break;
    }

    return Expression.Lambda<Func<T, bool>>(expressionBody, new ParameterExpression[] { parameterExpression });
}

private static MethodCallExpression GetLowerCasePropertyAccess(MemberExpression propertyAccess)
{
    var stringExpression = GetConvertToStringExpression(propertyAccess);
    if (stringExpression == null)
        throw new Exception(string.Format("Not supported property type {0}", propertyAccess.Type));

    return Expression.Call(stringExpression, typeof(string).GetMethod("ToLower", Type.EmptyTypes));
}

private static Expression GetConvertToStringExpression(Expression e)
{
    // if property string - no cast needed
    // else - use SqlFunction.StringConvert(double?) or SqlFunction.StringConvert(decimal?);
    Expression strExpression = null;
    if (e.Type == typeof(string)) strExpression = e;
    else
    {
        var systemType = Nullable.GetUnderlyingType(e.Type) ?? e.Type;
        if (systemType == typeof(int) || systemType == typeof(long) || systemType == typeof(double) || systemType == typeof(short) || systemType == typeof(byte))
        {
            // cast int to double
            var doubleExpr = Expression.Convert(e, typeof(double?));
            strExpression = Expression.Call(StringConvertMethodDouble, doubleExpr);
        }
        else if (systemType == typeof(decimal))
        {
            // call decimal version of StringConvert method
            // cast to nullable decimal
            var decimalExpr = Expression.Convert(e, typeof(decimal?));
            strExpression = Expression.Call(StringConvertMethodDecimal, decimalExpr);
        }
    }
    return strExpression;
}

private static readonly MethodInfo ContainsMethod = typeof(String).GetMethod("Contains", new Type[] { typeof(String) });
private static readonly MethodInfo StringConvertMethodDouble = typeof(SqlFunctions).GetMethod("StringConvert", new Type[] { typeof(double?) });
private static readonly MethodInfo StringConvertMethodDecimal = typeof(SqlFunctions).GetMethod("StringConvert", new Type[] { typeof(decimal?) });

公共静态表达式创建（字符串propertyName、ComparisonOperators、comparisonOperator、dynamic CompariedValue1、dynamic CompariedValue2=null）
{
ParameterExpression ParameterExpression=Expression.Parameter（typeof（T），“x”）；
MemberExpression MemberExpression=Expression.MakeMemberAccess（parameterExpression，typeof（T）.GetProperty（propertyName））；
ConstantExpression ConstantExpression=Expression.Constant（comparedValue1，comparedValue1.GetType（））；
表达式expressionBody=null；
开关（比较运算符）
{
...
案例比较运算符。包含：
expressionBody=Expression.Call（GetLowerCasePropertyAccess（memberExpression），ContainsMethod，Expression.Constant（comparedValue1.ToLower（））；
打破
}
返回表达式.Lambda（expressionBody，新参数表达式[]{ParameterExpression}）；
}
私有静态方法CallExpression GetLowerCasePropertyAccess（MemberExpression propertyAccess）
{
var stringExpression=GetConvertToString表达式（propertyAccess）；
if（stringExpression==null）
抛出新异常（string.Format（“不支持的属性类型{0}”，propertyAccess.type））；
返回Expression.Call（stringExpression，typeof（string）.GetMethod（“ToLower”，Type.EmptyTypes））；
}
私有静态表达式GetConvertToString表达式（表达式e）
{
//如果属性字符串-不需要强制转换
//else-使用SqlFunction.StringConvert（double？）或SqlFunction.StringConvert（decimal？）；
表达式strExpression=null；
如果（e.Type==typeof（string））strExpression=e；
其他的
{
var systemType=Nullable.GetUnderlyingType（e.Type）？？e.Type；
如果（systemType==typeof（int）| | systemType==typeof（long）| | systemType==typeof（double）| | systemType==typeof（short）| | systemType==typeof（byte））
{
//将int转换为double
var doubleExpr=表达式.Convert（e，typeof（double？）；
strExpression=Expression.Call（StringConvertMethodDouble，doubleExpr）；
}
else if（systemType==typeof（十进制））
{
//调用StringConvert方法的十进制版本
//强制转换为可为空的十进制数
var decimalExpr=表达式.Convert（e，typeof（decimal？）；
strExpression=Expression.Call（StringConvertMethodDecimal，decimalExpr）；
}
}
回归表达；
}
私有静态只读方法info ContainsMethod=typeof（String）.GetMethod（“Contains”，新类型[]{typeof（String）}）；
私有静态只读MethodInfo StringConvertMethodDouble=typeof（SqlFunctions）.GetMethod（“StringConvert”，新类型[]{typeof（double？}）；
私有静态只读MethodInfo StringConvertMethodDecimal=typeof（SqlFunctions）.GetMethod（“StringConvert”，新类型[]{typeof（decimal？}）；

像这样：

ctx.Products.Where(x => SqlFunctions.PatIndex("%Something%", x.Name) > 1).ToList();

但这与：

ctx.Products.Where(x => x.Name.Contains("Something")).ToList();

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嗨，我需要知道如何构建表达式（在表达式体上方的中）。