我在SQL中有一个过程,我试图转化为Linq:

SELECT O.Id, O.Name as Organization
FROM Organizations O
JOIN OrganizationsHierarchy OH ON O.Id=OH.OrganizationsId
where OH.Hierarchy like '%/12/%'

我最关心的一行是:

where OH.Hierarchy like '%/12/%'

我有一个存储层次结构的列,例如/1/3/12/,所以我只使用%/12/%来搜索它。

我的问题是,Linq或。net中使用百分号的等价是什么?


当前回答

如果你不匹配数字字符串,最好使用通用大小写:

.Where(oh => oh.Hierarchy.ToUpper().Contains(mySearchString.ToUpper()))

其他回答

如果你不匹配数字字符串,最好使用通用大小写:

.Where(oh => oh.Hierarchy.ToUpper().Contains(mySearchString.ToUpper()))
.Where(oh => oh.Hierarchy.Contains("/12/"))

你也可以使用. startswith()或. endswith()。

用这个:

from c in dc.Organization
where SqlMethods.Like(c.Hierarchy, "%/12/%")
select *;

如果您需要为单元测试这样的客户端操作提供LIKE功能,CodeProject的这个方法很好地模拟了通配符的行为。

有点像@史蒂夫·阿克曼的回答,但更全面。

/// Published on CodeProject: http://www.codeproject.com/Articles/
///         608266/A-Csharp-LIKE-implementation-that-mimics-SQL-LIKE
/// </remarks>
public static bool Like(this string s, string match, bool CaseInsensitive = true)
{
    //Nothing matches a null mask or null input string
    if (match == null || s == null)
        return false;
    //Null strings are treated as empty and get checked against the mask.
    //If checking is case-insensitive we convert to uppercase to facilitate this.
    if (CaseInsensitive)
    {
        s = s.ToUpperInvariant();
        match = match.ToUpperInvariant();
    }
    //Keeps track of our position in the primary string - s.
    int j = 0;
    //Used to keep track of multi-character wildcards.
    bool matchanymulti = false;
    //Used to keep track of multiple possibility character masks.
    string multicharmask = null;
    bool inversemulticharmask = false;
    for (int i = 0; i < match.Length; i++)
    {
        //If this is the last character of the mask and its a % or * we are done
        if (i == match.Length - 1 && (match[i] == '%' || match[i] == '*'))
            return true;
        //A direct character match allows us to proceed.
        var charcheck = true;
        //Backslash acts as an escape character.  If we encounter it, proceed
        //to the next character.
        if (match[i] == '\\')
        {
            i++;
            if (i == match.Length)
                i--;
        }
        else
        {
            //If this is a wildcard mask we flag it and proceed with the next character
            //in the mask.
            if (match[i] == '%' || match[i] == '*')
            {
                matchanymulti = true;
                continue;
            }
            //If this is a single character wildcard advance one character.
            if (match[i] == '_')
            {
                //If there is no character to advance we did not find a match.
                if (j == s.Length)
                    return false;
                j++;
                continue;
            }
            if (match[i] == '[')
            {
                var endbracketidx = match.IndexOf(']', i);
                //Get the characters to check for.
                multicharmask = match.Substring(i + 1, endbracketidx - i - 1);
                //Check for inversed masks
                inversemulticharmask = multicharmask.StartsWith("^");
                //Remove the inversed mask character
                if (inversemulticharmask)
                    multicharmask = multicharmask.Remove(0, 1);
                //Unescape \^ to ^
                multicharmask = multicharmask.Replace("\\^", "^");
                
                //Prevent direct character checking of the next mask character
                //and advance to the next mask character.
                charcheck = false;
                i = endbracketidx;
                //Detect and expand character ranges
                if (multicharmask.Length == 3 && multicharmask[1] == '-')
                {
                    var newmask = "";
                    var first = multicharmask[0];
                    var last = multicharmask[2];
                    if (last < first)
                    {
                        first = last;
                        last = multicharmask[0];
                    }
                    var c = first;
                    while (c <= last)
                    {
                        newmask += c;
                        c++;
                    }
                    multicharmask = newmask;
                }
                //If the mask is invalid we cannot find a mask for it.
                if (endbracketidx == -1)
                    return false;
            }
        }
        //Keep track of match finding for this character of the mask.
        var matched = false;
        while (j < s.Length)
        {
            //This character matches, move on.
            if (charcheck && s[j] == match[i])
            {
                j++;
                matched = true;
                break;
            }
            //If we need to check for multiple charaters to do.
            if (multicharmask != null)
            {
                var ismatch = multicharmask.Contains(s[j]);
                //If this was an inverted mask and we match fail the check for this string.
                //If this was not an inverted mask check and we did not match fail for this string.
                if (inversemulticharmask && ismatch ||
                    !inversemulticharmask && !ismatch)
                {
                    //If we have a wildcard preceding us we ignore this failure
                    //and continue checking.
                    if (matchanymulti)
                    {
                        j++;
                        continue;
                    }
                    return false;
                }
                j++;
                matched = true;
                //Consumse our mask.
                multicharmask = null;
                break;
            }
            //We are in an multiple any-character mask, proceed to the next character.
            if (matchanymulti)
            {
                j++;
                continue;
            }
            break;
        }
        //We've found a match - proceed.
        if (matched)
        {
            matchanymulti = false;
            continue;
        }

        //If no match our mask fails
        return false;
    }
    //Some characters are left - our mask check fails.
    if (j < s.Length)
        return false;
    //We've processed everything - this is a match.
    return true;
} 

如果你使用VB。NET,那么答案将是“*”。这是你的where从句的样子…

Where OH.Hierarchy Like '*/12/*'

备注:“*”匹配零个或多个字符。下面是关于Like操作符的msdn文章。