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问类型“string”不能用作类型参数“TValue”，没有从“string”到“System.IFormattable”的隐式引用转换
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Stack Overflow用户

提问于 2021-10-03 05:06:35

回答 3查看 59关注 0票数 0

我有一个问题，这是我的代码片段

        using System;
        using System.IO;
        using CsvHelper;
        using System.Xml;
        using System.Linq;
        using System.Xml.Linq;
        using Newtonsoft.Json;
        using System.Collections;
        using System.Globalization;
        using CsvHelper.Configuration;
        using System.Collections.Generic;
        using System.Runtime.InteropServices;

        namespace MXPSQL.EDict{
            public class CvsStuff{
                public CsvConfiguration cvscfg = new CsvConfiguration(CultureInfo.InvariantCulture)
                {
                    NewLine = Environment.NewLine,
                    PrepareHeaderForMatch = args => args.Header.ToLower(),
                    Comment = '#'
                };
            }
            // extensible dictionary
            public class ExtDictionary<TKey, TValue> : Dictionary<TKey, TValue> where TValue : ICloneable
            {
                // original code
                /*
                    public CloneableDictionary<TKey, TValue> Clone()
                        {
                        CloneableDictionary<TKey, TValue> clone = new CloneableDictionary<TKey, TValue>();
                        foreach (KeyValuePair<TKey, TValue> kvp in this)
                            {
                            clone.Add(kvp.Key, (TValue) kvp.Value.Clone());
                            }
                        return clone;
                        }
                */

                public readonly CvsStuff cvss = new CvsStuff();

                // new one
                public ExtDictionary<TKey, TValue> New()
                {
                    ExtDictionary<TKey, TValue> clone = new ExtDictionary<TKey, TValue>();
                    foreach (KeyValuePair<TKey, TValue> kvp in this)
                    {
                        clone.Add(kvp.Key, (TValue) kvp.Value.Clone());
                    }
                    return clone;
                }

                // extended code
                public ExtDictionary<TKey, TValue> Clone(){
                    return New();
                }

                // convert from other to this
                public void ConvertFromDictionary(Dictionary<TKey, TValue> dict){
                    foreach (KeyValuePair<TKey, TValue> kvp in dict){
                        this.Add(kvp.Key, (TValue) kvp.Value.Clone());
                    }
                }

                public void ConvertFromKeyValuePair(KeyValuePair<TKey, TValue> kvpx){
                    var list = new List<KeyValuePair<TKey, TValue>>{kvpx};
                    var dict = list.ToDictionary(x => x.Key, x => x.Value);
                    // dict.Add(kvpx.Key, kvpx.Value.Clone());
                    /* foreach (KeyValuePair<TKey, TValue> kvp in kvpx){
                        this.Add(kvp.Key, (TValue) kvp.Value.Clone());
                    } */
                    ConvertFromDictionary(dict);
                }

                public void ConvertFromJson(string json){
                    Dictionary<TKey, TValue> dict = JsonConvert.DeserializeObject<Dictionary<TKey, TValue>>(json);

                    ConvertFromDictionary(dict);
                }

                /* public void ConvertFromCsv(string csvtr){
                    string res = "";
                    IEnumerable<T> IEBuffer;
                    ILookup<string, Order> Lookup;
                    using(var sreader = new StringReader(res))
                    using (var csv = new CsvReader(sreader, cvss.cvscfg))
                    {
                        // csv.WriteRecords(this);
                        IEBuffer = csv.GetRecords<T>;
                        Lookup = IEBuffer.ToLookup(o => o.CustomerName);
                    }

                    this = Lookup.ToDictionary(g => g.Key);
                } */

                /* public void ConvertFromCvs(string cvstr){
                    ConvertFromCsv(cvstr);
                } */

                // convert from this to others
                public Dictionary<TKey, TValue> ToDictionary(){
                    Dictionary<TKey, TValue> NewDict = new Dictionary<TKey, TValue>();
                    ExtDictionary<TKey, TValue> edict = this.New();
                    foreach(KeyValuePair<TKey, TValue> kvp in edict){
                        NewDict.Add(kvp.Key, (TValue) kvp.Value.Clone());
                    }
                    return NewDict;
                }

                public List<KeyValuePair<TKey, TValue>> ToLKVP(){
                    var list = this.ToList<KeyValuePair<TKey, TValue>>();

                    return list;
                }

                public string ToJson(){
                    var strs = JsonConvert.SerializeObject(this, Newtonsoft.Json.Formatting.Indented);

                    return strs;
                }

                public string ToCsv(){
                    string res = "";

                    using(var swriter = new StringWriter()){
                        using (var csv = new CsvWriter(swriter, cvss.cvscfg))
                        {
                            csv.WriteRecords(this);
                        }
                        res = swriter.ToString();
                    }

                    return res;
                }

                public string ToCvs(){
                    return ToCsv();
                }

                public string ToXML(){
                    string json = ToJson();
                    XNode node = JsonConvert.DeserializeXNode(json, "Root");
                    return node.ToString();
                }

                public string ToXml(){
                    return ToXML();
                }
            }
        }

下面是有问题的代码

          static ExtDictionary<string, string> TemplaeDict = new ExtDictionary<string, string>();
          static ExtDictionary<string, string> JSONDict = TemplaeDict.New();

当运行"dotnet build“时，我得到这个错误。

C:\snek\Program.cs(151,40): error CS0311: The type 'string' cannot be used as type parameter 'TValue' in the generic type or method 'ExtDictionary<TKey, TValue>'. There is no implicit reference conversion from 'string' to 'System.IFormattable'. [C:\snek\snek.csproj]

C:\snek\Program.cs(152,40): error CS0311: The type 'string' cannot be used as type parameter 'TValue' in the generic type or method 'ExtDictionary<TKey, TValue>'. There is no implicit reference conversion from 'string' to 'System.IFormattable'. [C:\snek\snek.csproj]

有没有人能帮我写一下代码，是不是主要代码有问题，或者是法令我看了看，没有很好的答案。

以下是The reference of the game The nuget code的一些链接

回答 3

Stack Overflow用户

回答已采纳

发布于 2021-10-04 23:37:28

using System;
using System.IO;
using CsvHelper;
using System.Xml;
using System.Linq;
using System.Xml.Linq;
using Newtonsoft.Json;
using System.Collections;
using System.Globalization;
using CsvHelper.Configuration;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace MXPSQL.EDict{
    public class CvsStuff{
        public CsvConfiguration cvscfg = new CsvConfiguration(CultureInfo.InvariantCulture)
        {
            NewLine = Environment.NewLine,
            PrepareHeaderForMatch = args => args.Header.ToLower(),
            Comment = '#'
        };
    }
    // extensible dictionary
    public class ExtDictionary<TKey, TValue> : Dictionary<TKey, TValue>, IFormattable where TValue : ICloneable
    {
        // original code
        /*
            public CloneableDictionary<TKey, TValue> Clone()
                {
                CloneableDictionary<TKey, TValue> clone = new CloneableDictionary<TKey, TValue>();
                foreach (KeyValuePair<TKey, TValue> kvp in this)
                    {
                    clone.Add(kvp.Key, (TValue) kvp.Value.Clone());
                    }
                return clone;
                }
        */

        public readonly CvsStuff cvss = new CvsStuff();

        // new one
        public ExtDictionary<TKey, TValue> New()
        {
            ExtDictionary<TKey, TValue> clone = new ExtDictionary<TKey, TValue>();
            foreach (KeyValuePair<TKey, TValue> kvp in this)
            {
                clone.Add(kvp.Key, (TValue) kvp.Value.Clone());
            }
            return clone;
        }

        // extended code
        public ExtDictionary<TKey, TValue> Clone(){
            return New();
        }

        // convert from other to this
        public void ConvertFromDictionary(Dictionary<TKey, TValue> dict){
            foreach (KeyValuePair<TKey, TValue> kvp in dict){
                this.Add(kvp.Key, (TValue) kvp.Value.Clone());
            }
        }

        public void ConvertFromKeyValuePair(KeyValuePair<TKey, TValue> kvpx){
            var list = new List<KeyValuePair<TKey, TValue>>{kvpx};
            var dict = list.ToDictionary(x => x.Key, x => x.Value);
            // dict.Add(kvpx.Key, kvpx.Value.Clone());
            /* foreach (KeyValuePair<TKey, TValue> kvp in kvpx){
                this.Add(kvp.Key, (TValue) kvp.Value.Clone());
            } */
            ConvertFromDictionary(dict);
        }

        public void ConvertFromJson(string json){
            Dictionary<TKey, TValue> dict = JsonConvert.DeserializeObject<Dictionary<TKey, TValue>>(json);

            ConvertFromDictionary(dict);
        }

        /* public void ConvertFromCsv(string csvtr){
            string res = "";
            IEnumerable<T> IEBuffer;
            ILookup<string, Order> Lookup;
            using(var sreader = new StringReader(res))
            using (var csv = new CsvReader(sreader, cvss.cvscfg))
            {
                // csv.WriteRecords(this);
                IEBuffer = csv.GetRecords<T>;
                Lookup = IEBuffer.ToLookup(o => o.CustomerName);
            }

            this = Lookup.ToDictionary(g => g.Key);
        } */

        /* public void ConvertFromCvs(string cvstr){
            ConvertFromCsv(cvstr);
        } */

        // convert from this to others
        public Dictionary<TKey, TValue> ToDictionary(){
            Dictionary<TKey, TValue> NewDict = new Dictionary<TKey, TValue>();
            ExtDictionary<TKey, TValue> edict = this.New();
            foreach(KeyValuePair<TKey, TValue> kvp in edict){
                NewDict.Add(kvp.Key, (TValue) kvp.Value.Clone());
            }
            return NewDict;
        }

        public List<KeyValuePair<TKey, TValue>> ToLKVP(){
            var list = this.ToList<KeyValuePair<TKey, TValue>>();

            return list;
        }

        public string ToJson(){
            var strs = JsonConvert.SerializeObject(this, Newtonsoft.Json.Formatting.Indented);

            return strs;
        }

        public string ToCsv(){
            string res = "";

            using(var swriter = new StringWriter()){
                using (var csv = new CsvWriter(swriter, cvss.cvscfg))
                {
                    csv.WriteRecords(this);
                }
                res = swriter.ToString();
            }

            return res;
        }

        public string ToCvs(){
            return ToCsv();
        }

        public string ToString(string? format, IFormatProvider? formatProvider){
            return ToCvs();
        }

        public string ToXML(){
            string json = ToJson();
            XNode node = JsonConvert.DeserializeXNode(json, "Root");
            return node.ToString();
        }

        public string ToXml(){
            return ToXML();
        }
    }
}

一个非常简单的解决方法，只需将I格式表移到where之前。问题是iformattable放在TValue上，而不是整个类上。

票数 0

Stack Overflow用户

发布于 2021-10-03 05:12:01

尝试使用FormattableString而不是string。参考：Difference between String, FormattableString, IFormattable

票数 1

Stack Overflow用户

发布于 2021-10-03 06:11:55

看起来没问题。您是否使用了另一个ExtDictionary类(同名但不同的命名空间/模块)？

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/69422222

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