Conversion of string to type Double is invalid

Hello Experts,

When I try to build a string based on the datatable and datarow

I am getting an error
"Conversion from string "'" to type 'Double' is not valid."

I am not converting anything to Double I am just building the string

Please help


Dim EroleIDs as string
EroleIDs="" 
For Each dr In dtEroles.Rows
                    If EroleIDs.Length > 0 Then EroleIDs += ","
                    EroleIDs = +"'" + dtEroles.Rows(0)(0).ToString() + "'"
                Next

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rowmarkAsked:
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prairiedogConnect With a Mentor Commented:
>>>EroleIDs = +"'" + dtEroles.Rows(0)(0).ToString() + "'"
It may be caused by the =+ operation in the above line.
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David H.H.LeeCommented:
Hi rowmark,
Try use "&" sign instead of "+" for the string combinations.
eg:
For Each dr In dtEroles.Rows
                    If EroleIDs.Length > 0 Then EroleIDs &= ","
                    EroleIDs &= "'" & dtEroles.Rows(0)(0).ToString() & "'"
                Next
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DreamsTechCommented:
I wrote a sample code : which worked correctly ,so it will double gets converted into string. The only reason it fails when the vulue you are trying to convert is not a number Or a null value
Dim str As String = ""
 Dim dt As New DataTable
        dt.Columns.Add("test")
        Dim dr As DataRow
        dr = dt.NewRow()
        dr("test") = "DoubleString"
        dt.Rows.Add(dr)
 
For Each dr1 As DataRow In dt.Rows
            str += str + "'" + dr1(0).ToString() + "'"
        Next

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DreamsTechCommented:
Ingnore my decs ,the only i thing i wanted to convey is ,the above code works fine ,still i in your foreach loop u looping the same row again n again ,the correct syntax wud be

or Each dr In dtEroles.Rows
                    If EroleIDs.Length > 0 Then EroleIDs += ","
                    EroleIDs = +"'" +  dr(0).ToString() + "'"  
                Next

try correcting this and let me know if this helps
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channa_mCommented:

 Try

dr(0).ToString() instead of   dtEroles.Rows(0)(0).ToString()
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